diff --git a/src/lib/config.h.in b/src/lib/config.h.in
index 5a9396e3..0e938e9b 100644
--- a/src/lib/config.h.in
+++ b/src/lib/config.h.in
@@ -73,3 +73,10 @@
     ((defined(__clang__) && (__clang_major__ >= 4)) )
 #define RNP_USE_STD_REGEX 1
 #endif
+
+/* do not use the statement for old MSVC versions */
+#if (!defined(_MSVC_LANG) || _MSVC_LANG >= 201703L)
+# define FALLTHROUGH_STATEMENT [[fallthrough]];
+#else
+# define FALLTHROUGH_STATEMENT
+#endif
\ No newline at end of file
diff --git a/src/lib/crypto.cpp b/src/lib/crypto.cpp
index 876ea117..59126b69 100644
--- a/src/lib/crypto.cpp
+++ b/src/lib/crypto.cpp
@@ -133,9 +133,7 @@ pgp_generate_seckey(const rnp_keygen_crypto_params_t &crypto,
             seckey.material.ec.curve = crypto.ecc.curve;
             break;
         }
-#if (!defined(_MSVC_LANG) || _MSVC_LANG >= 201703L)
-        [[fallthrough]];
-#endif
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_ECDSA:
     case PGP_PKA_SM2:
         if (!curve_supported(crypto.ecc.curve)) {
@@ -175,14 +173,14 @@ pgp_generate_seckey(const rnp_keygen_crypto_params_t &crypto,
 #endif
 #if defined(ENABLE_PQC)
     case PGP_PKA_KYBER768_X25519:
-        [[fallthrough]];
-    // TODO add case PGP_PKA_KYBER1024_X448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO add case PGP_PKA_KYBER1024_X448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_BP384:
         if (pgp_kyber_ecdh_composite_key_t::gen_keypair(
               &crypto.ctx->rng, &seckey.material.kyber_ecdh, seckey.alg)) {
@@ -191,14 +189,14 @@ pgp_generate_seckey(const rnp_keygen_crypto_params_t &crypto,
         }
         break;
     case PGP_PKA_DILITHIUM3_ED25519:
-        [[fallthrough]];
-    // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_BP384:
         if (pgp_dilithium_exdsa_composite_key_t::gen_keypair(
               &crypto.ctx->rng, &seckey.material.dilithium_exdsa, seckey.alg)) {
@@ -208,7 +206,7 @@ pgp_generate_seckey(const rnp_keygen_crypto_params_t &crypto,
         }
         break;
     case PGP_PKA_SPHINCSPLUS_SHA2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHAKE:
         if (pgp_sphincsplus_generate(&crypto.ctx->rng,
                                      &seckey.material.sphincsplus,
@@ -267,29 +265,29 @@ key_material_equal(const pgp_key_material_t *key1, const pgp_key_material_t *key
 #endif
 #if defined(ENABLE_PQC)
     case PGP_PKA_KYBER768_X25519:
-        [[fallthrough]];
-    // TODO add case PGP_PKA_KYBER1024_X448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO add case PGP_PKA_KYBER1024_X448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_BP384:
         return (key1->kyber_ecdh.pub == key2->kyber_ecdh.pub);
     case PGP_PKA_DILITHIUM3_ED25519:
-        [[fallthrough]];
-    // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_BP384:
         return (key1->dilithium_exdsa.pub == key2->dilithium_exdsa.pub);
     case PGP_PKA_SPHINCSPLUS_SHA2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHAKE:
         return (key1->sphincsplus.pub == key2->sphincsplus.pub);
 #endif
@@ -348,29 +346,29 @@ validate_pgp_key_material(const pgp_key_material_t *material, rnp::RNG *rng)
 #endif
 #if defined(ENABLE_PQC)
     case PGP_PKA_KYBER768_X25519:
-        [[fallthrough]];
-    // TODO add case PGP_PKA_KYBER1024_X448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO add case PGP_PKA_KYBER1024_X448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_BP384:
         return kyber_ecdh_validate_key(rng, &material->kyber_ecdh, material->secret);
     case PGP_PKA_DILITHIUM3_ED25519:
-        [[fallthrough]];
-    // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_BP384:
         return dilithium_exdsa_validate_key(rng, &material->dilithium_exdsa, material->secret);
     case PGP_PKA_SPHINCSPLUS_SHA2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHAKE:
         return sphincsplus_validate_key(rng, &material->sphincsplus, material->secret);
 #endif
diff --git a/src/lib/crypto/dilithium_exdsa_composite.cpp b/src/lib/crypto/dilithium_exdsa_composite.cpp
index 116d7597..cd2ed80c 100644
--- a/src/lib/crypto/dilithium_exdsa_composite.cpp
+++ b/src/lib/crypto/dilithium_exdsa_composite.cpp
@@ -142,16 +142,14 @@ pgp_dilithium_exdsa_composite_key_t::pk_alg_to_dilithium_id(pgp_pubkey_alg_t pk_
 {
     switch (pk_alg) {
     case PGP_PKA_DILITHIUM3_ED25519:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_BP256:
         return dilithium_L3;
     case PGP_PKA_DILITHIUM5_BP384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_P384:
-        //[[fallthrough]];
-        // case PGP_PKA_DILITHIUM5_ED448:
         return dilithium_L5;
     default:
         RNP_LOG("invalid PK alg given");
diff --git a/src/lib/crypto/ec.cpp b/src/lib/crypto/ec.cpp
index ef937350..8aca0a47 100644
--- a/src/lib/crypto/ec.cpp
+++ b/src/lib/crypto/ec.cpp
@@ -199,17 +199,17 @@ is_generic_prime_curve(pgp_curve_t curve)
 {
     switch (curve) {
     case PGP_CURVE_NIST_P_256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_CURVE_NIST_P_384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_CURVE_NIST_P_521:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_CURVE_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_CURVE_BP384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_CURVE_BP512:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_CURVE_P256K1:
         return true;
     default:
diff --git a/src/lib/crypto/ecdh.cpp b/src/lib/crypto/ecdh.cpp
index 85a0b637..31f078ac 100644
--- a/src/lib/crypto/ecdh.cpp
+++ b/src/lib/crypto/ecdh.cpp
@@ -412,17 +412,17 @@ exdsa_gen_keypair_native(rnp::RNG *            rng,
         alg = PGP_PKA_EDDSA;
         break;
     case PGP_CURVE_NIST_P_256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_CURVE_NIST_P_384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_CURVE_NIST_P_521:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_CURVE_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_CURVE_BP384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_CURVE_BP512:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_CURVE_P256K1:
         alg = PGP_PKA_ECDSA;
         break;
diff --git a/src/lib/crypto/kyber_ecdh_composite.cpp b/src/lib/crypto/kyber_ecdh_composite.cpp
index 01ac337f..b6955621 100644
--- a/src/lib/crypto/kyber_ecdh_composite.cpp
+++ b/src/lib/crypto/kyber_ecdh_composite.cpp
@@ -170,16 +170,14 @@ pgp_kyber_ecdh_composite_key_t::pk_alg_to_kyber_id(pgp_pubkey_alg_t pk_alg)
 {
     switch (pk_alg) {
     case PGP_PKA_KYBER768_X25519:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_BP256:
         return kyber_768;
     case PGP_PKA_KYBER1024_BP384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_P384:
-        //[[fallthrough]];
-        // case PGP_PKA_KYBER1024_X448:
         return kyber_1024;
     default:
         RNP_LOG("invalid PK alg given");
diff --git a/src/lib/crypto/signatures.cpp b/src/lib/crypto/signatures.cpp
index e4dcf9b1..8255ca68 100644
--- a/src/lib/crypto/signatures.cpp
+++ b/src/lib/crypto/signatures.cpp
@@ -196,20 +196,20 @@ signature_calculate(pgp_signature_t &     sig,
     }
 #if defined(ENABLE_PQC)
     case PGP_PKA_DILITHIUM3_ED25519:
-        [[fallthrough]];
-    // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_BP384:
         ret = seckey.dilithium_exdsa.priv.sign(
           &ctx.rng, &material.dilithium_exdsa, hash_alg, hval, hlen);
         break;
     case PGP_PKA_SPHINCSPLUS_SHA2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHAKE:
         ret = seckey.sphincsplus.priv.sign(&ctx.rng, &material.sphincsplus, hval, hlen);
         break;
@@ -256,7 +256,7 @@ signature_validate(const pgp_signature_t &     sig,
     bool hash_alg_valid = false;
     switch (key.alg) {
     case PGP_PKA_SPHINCSPLUS_SHA2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHAKE:
         hash_alg_valid = key.sphincsplus.pub.validate_signature_hash_requirements(hash.alg());
         break;
@@ -339,20 +339,20 @@ signature_validate(const pgp_signature_t &     sig,
         break;
 #if defined(ENABLE_PQC)
     case PGP_PKA_DILITHIUM3_ED25519:
-        [[fallthrough]];
-    // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_BP384:
         ret =
           key.dilithium_exdsa.pub.verify(&material.dilithium_exdsa, hash.alg(), hval, hlen);
         break;
     case PGP_PKA_SPHINCSPLUS_SHA2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHAKE:
         ret = key.sphincsplus.pub.verify(&material.sphincsplus, hval, hlen);
         break;
diff --git a/src/lib/crypto/sphincsplus.cpp b/src/lib/crypto/sphincsplus.cpp
index ea212276..5589212e 100644
--- a/src/lib/crypto/sphincsplus.cpp
+++ b/src/lib/crypto/sphincsplus.cpp
@@ -338,18 +338,18 @@ sphincsplus_hash_allowed(pgp_pubkey_alg_t        pk_alg,
     case PGP_PKA_SPHINCSPLUS_SHA2:
         switch (sphincsplus_param) {
         case sphincsplus_simple_128s:
-            [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
         case sphincsplus_simple_128f:
             if (hash_alg != PGP_HASH_SHA256) {
                 return false;
             }
             break;
         case sphincsplus_simple_192s:
-            [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
         case sphincsplus_simple_192f:
-            [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
         case sphincsplus_simple_256s:
-            [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
         case sphincsplus_simple_256f:
             if (hash_alg != PGP_HASH_SHA512) {
                 return false;
@@ -360,18 +360,18 @@ sphincsplus_hash_allowed(pgp_pubkey_alg_t        pk_alg,
     case PGP_PKA_SPHINCSPLUS_SHAKE:
         switch (sphincsplus_param) {
         case sphincsplus_simple_128s:
-            [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
         case sphincsplus_simple_128f:
             if (hash_alg != PGP_HASH_SHA3_256) {
                 return false;
             }
             break;
         case sphincsplus_simple_192s:
-            [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
         case sphincsplus_simple_192f:
-            [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
         case sphincsplus_simple_256s:
-            [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
         case sphincsplus_simple_256f:
             if (hash_alg != PGP_HASH_SHA3_512) {
                 return false;
diff --git a/src/lib/fingerprint.cpp b/src/lib/fingerprint.cpp
index b6464ebb..a1b002d4 100644
--- a/src/lib/fingerprint.cpp
+++ b/src/lib/fingerprint.cpp
@@ -60,7 +60,7 @@ pgp_fingerprint(pgp_fingerprint_t &fp, const pgp_key_pkt_t &key)
     switch (key.version) {
 #if defined(ENABLE_CRYPTO_REFRESH)
     case PGP_V6:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
 #endif
     case PGP_V4:
         break;
diff --git a/src/lib/generate-key.cpp b/src/lib/generate-key.cpp
index 88e02e4d..52481f97 100644
--- a/src/lib/generate-key.cpp
+++ b/src/lib/generate-key.cpp
@@ -282,29 +282,29 @@ get_numbits(const rnp_keygen_crypto_params_t *crypto)
         return crypto->elgamal.key_bitlen;
 #if defined(ENABLE_PQC)
     case PGP_PKA_KYBER768_X25519:
-        [[fallthrough]];
-    // TODO add case PGP_PKA_KYBER1024_X448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO add case PGP_PKA_KYBER1024_X448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_BP384:
         return pgp_kyber_ecdh_composite_public_key_t::encoded_size(crypto->key_alg) * 8;
     case PGP_PKA_DILITHIUM3_ED25519:
-        [[fallthrough]];
-    // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_BP384:
         return pgp_dilithium_exdsa_composite_public_key_t::encoded_size(crypto->key_alg) * 8;
     case PGP_PKA_SPHINCSPLUS_SHA2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHAKE:
         return sphincsplus_pubkey_size(crypto->sphincsplus.param) * 8;
 #endif
@@ -359,7 +359,7 @@ pgp_check_key_hash_requirements(rnp_keygen_crypto_params_t &crypto)
 {
     switch (crypto.key_alg) {
     case PGP_PKA_SPHINCSPLUS_SHA2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHAKE:
         if (!sphincsplus_hash_allowed(
               crypto.key_alg, crypto.sphincsplus.param, crypto.hash_alg)) {
@@ -367,14 +367,14 @@ pgp_check_key_hash_requirements(rnp_keygen_crypto_params_t &crypto)
         }
         break;
     case PGP_PKA_DILITHIUM3_ED25519:
-        [[fallthrough]];
-    // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_BP384:
         if (!dilithium_hash_allowed(crypto.hash_alg)) {
             return false;
diff --git a/src/lib/pgp-key.cpp b/src/lib/pgp-key.cpp
index 58e62eef..99f21ab9 100644
--- a/src/lib/pgp-key.cpp
+++ b/src/lib/pgp-key.cpp
@@ -209,30 +209,30 @@ pgp_pk_alg_capabilities(pgp_pubkey_alg_t alg)
 
 #if defined(ENABLE_PQC)
     case PGP_PKA_KYBER768_X25519:
-        [[fallthrough]];
-    // TODO add case PGP_PKA_KYBER1024_X448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO add case PGP_PKA_KYBER1024_X448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_BP384:
         return PGP_KF_ENCRYPT;
 
     case PGP_PKA_DILITHIUM3_ED25519:
-        [[fallthrough]];
-    // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_BP384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHA2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHAKE:
         return pgp_key_flags_t(PGP_KF_SIGN | PGP_KF_CERTIFY | PGP_KF_AUTH);
 #endif
@@ -2783,11 +2783,11 @@ pgp_key_material_t::curve() const
 {
     switch (alg) {
     case PGP_PKA_ECDH:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_ECDSA:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_EDDSA:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SM2:
         return ec.curve;
 #if defined(ENABLE_CRYPTO_REFRESH)
@@ -2815,16 +2815,16 @@ pgp_key_material_t::bits() const
     case PGP_PKA_ELGAMAL_ENCRYPT_OR_SIGN:
         return 8 * mpi_bytes(&eg.y);
     case PGP_PKA_ECDH:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_ECDSA:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_EDDSA:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
 #if defined(ENABLE_CRYPTO_REFRESH)
     case PGP_PKA_ED25519:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_X25519:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
 #endif
     case PGP_PKA_SM2: {
         /* handle ecc cases */
@@ -2833,29 +2833,29 @@ pgp_key_material_t::bits() const
     }
 #if defined(ENABLE_PQC)
     case PGP_PKA_KYBER768_X25519:
-        [[fallthrough]];
-    // TODO add case PGP_PKA_KYBER1024_X448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO add case PGP_PKA_KYBER1024_X448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_BP384:
         return 8 * kyber_ecdh.pub.get_encoded().size(); /* public key length */
     case PGP_PKA_DILITHIUM3_ED25519:
-        [[fallthrough]];
-    // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_BP384:
         return 8 * dilithium_exdsa.pub.get_encoded().size(); /* public key length*/
     case PGP_PKA_SPHINCSPLUS_SHA2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHAKE:
         return 8 * sphincsplus.pub.get_encoded().size(); /* public key length */
 #endif
diff --git a/src/lib/rnp.cpp b/src/lib/rnp.cpp
index bfe81165..11ea7ec5 100644
--- a/src/lib/rnp.cpp
+++ b/src/lib/rnp.cpp
@@ -5266,29 +5266,29 @@ default_key_flags(pgp_pubkey_alg_t alg, bool subkey)
 #endif
 #if defined(ENABLE_PQC)
     case PGP_PKA_KYBER768_X25519:
-        [[fallthrough]];
-    // TODO add case PGP_PKA_KYBER1024_X448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO add case PGP_PKA_KYBER1024_X448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_BP384:
         return PGP_KF_ENCRYPT;
     case PGP_PKA_DILITHIUM3_ED25519:
-        [[fallthrough]];
-    // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_BP384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHA2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHAKE:
         return subkey ? PGP_KF_SIGN : pgp_key_flags_t(PGP_KF_SIGN | PGP_KF_CERTIFY);
 #endif
@@ -7548,29 +7548,29 @@ add_json_public_mpis(json_object *jso, pgp_key_t *key)
 #endif
 #if defined(ENABLE_PQC)
     case PGP_PKA_KYBER768_X25519:
-        [[fallthrough]];
-    // TODO add case PGP_PKA_KYBER1024_X448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO add case PGP_PKA_KYBER1024_X448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_BP384:
         return RNP_SUCCESS; /* TODO */
     case PGP_PKA_DILITHIUM3_ED25519:
-        [[fallthrough]];
-    // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_BP384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHA2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHAKE:
         return RNP_SUCCESS; /* TODO */
 #endif
@@ -7607,14 +7607,14 @@ add_json_secret_mpis(json_object *jso, pgp_key_t *key)
 #endif
 #if defined(ENABLE_PQC)
     case PGP_PKA_KYBER768_X25519:
-        [[fallthrough]];
-    // TODO add case PGP_PKA_KYBER1024_X448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO add case PGP_PKA_KYBER1024_X448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_BP384:
         return RNP_SUCCESS; /* TODO */
 #endif
@@ -7657,18 +7657,18 @@ add_json_sig_mpis(json_object *jso, const pgp_signature_t *sig)
 #endif
 #if defined(ENABLE_PQC)
     case PGP_PKA_DILITHIUM3_ED25519:
-        [[fallthrough]];
-    // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_BP384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHA2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHAKE:
         return RNP_SUCCESS; /* TODO */
 #endif
@@ -7874,10 +7874,7 @@ key_to_json(json_object *jso, rnp_key_handle_t handle, uint32_t flags)
             return RNP_ERROR_OUT_OF_MEMORY;
         }
     }
-
-#if (!defined(_MSVC_LANG) || _MSVC_LANG >= 201703L)
-        [[fallthrough]];
-#endif
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_ECDSA:
     case PGP_PKA_EDDSA:
     case PGP_PKA_SM2: {
@@ -7896,29 +7893,29 @@ key_to_json(json_object *jso, rnp_key_handle_t handle, uint32_t flags)
 #endif
 #if defined(ENABLE_PQC)
     case PGP_PKA_KYBER768_X25519:
-        [[fallthrough]];
-    // TODO add case PGP_PKA_KYBER1024_X448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO add case PGP_PKA_KYBER1024_X448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_BP384:
         return RNP_SUCCESS; /* TODO */
     case PGP_PKA_DILITHIUM3_ED25519:
-        [[fallthrough]];
-    // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_BP384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHA2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHAKE:
         return RNP_SUCCESS; /* TODO */
 #endif
diff --git a/src/librekey/rnp_key_store.cpp b/src/librekey/rnp_key_store.cpp
index 2af71534..0918d155 100644
--- a/src/librekey/rnp_key_store.cpp
+++ b/src/librekey/rnp_key_store.cpp
@@ -749,31 +749,31 @@ rnp_key_store_get_key_grip(const pgp_key_material_t *key, pgp_key_grip_t &grip)
 #endif
 #if defined(ENABLE_PQC)
         case PGP_PKA_KYBER768_X25519:
-            [[fallthrough]];
-        // TODO add case PGP_PKA_KYBER1024_X448: [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
+        // TODO add case PGP_PKA_KYBER1024_X448: FALLTHROUGH_STATEMENT;
         case PGP_PKA_KYBER768_P256:
-            [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
         case PGP_PKA_KYBER1024_P384:
-            [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
         case PGP_PKA_KYBER768_BP256:
-            [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
         case PGP_PKA_KYBER1024_BP384:
             hash->add(key->kyber_ecdh.pub.get_encoded());
             break;
         case PGP_PKA_DILITHIUM3_ED25519:
-            [[fallthrough]];
-        // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
+        // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
         case PGP_PKA_DILITHIUM3_P256:
-            [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
         case PGP_PKA_DILITHIUM5_P384:
-            [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
         case PGP_PKA_DILITHIUM3_BP256:
-            [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
         case PGP_PKA_DILITHIUM5_BP384:
             hash->add(key->dilithium_exdsa.pub.get_encoded());
             break;
         case PGP_PKA_SPHINCSPLUS_SHA2:
-            [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
         case PGP_PKA_SPHINCSPLUS_SHAKE:
             hash->add(key->sphincsplus.pub.get_encoded());
             break;
diff --git a/src/librepgp/stream-dump.cpp b/src/librepgp/stream-dump.cpp
index 30cd1ff0..644af5b6 100644
--- a/src/librepgp/stream-dump.cpp
+++ b/src/librepgp/stream-dump.cpp
@@ -828,20 +828,20 @@ stream_dump_signature_pkt(rnp_dump_ctx_t *ctx, pgp_signature_t *sig, pgp_dest_t
 #endif
 #if defined(ENABLE_PQC)
     case PGP_PKA_DILITHIUM3_ED25519:
-        [[fallthrough]];
-    // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_BP384:
         dst_print_vec(
           dst, "dilithium-ecdsa/eddsa sig", material.dilithium_exdsa.sig, ctx->dump_mpi);
         break;
     case PGP_PKA_SPHINCSPLUS_SHA2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHAKE:
         dst_print_vec(dst, "sphincs+ sig", material.sphincsplus.sig, ctx->dump_mpi);
         break;
@@ -950,14 +950,14 @@ stream_dump_key(rnp_dump_ctx_t *ctx, pgp_source_t *src, pgp_dest_t *dst)
 #endif
 #if defined(ENABLE_PQC)
     case PGP_PKA_KYBER768_X25519:
-        [[fallthrough]];
-    // TODO add case PGP_PKA_KYBER1024_X448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO add case PGP_PKA_KYBER1024_X448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_BP384:
         dst_print_vec(dst,
                       "kyber-ecdh encoded pubkey",
@@ -965,14 +965,14 @@ stream_dump_key(rnp_dump_ctx_t *ctx, pgp_source_t *src, pgp_dest_t *dst)
                       ctx->dump_mpi);
         break;
     case PGP_PKA_DILITHIUM3_ED25519:
-        [[fallthrough]];
-    // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_BP384:
         dst_print_vec(dst,
                       "dilithium-ecdsa/eddsa encodced pubkey",
@@ -980,7 +980,7 @@ stream_dump_key(rnp_dump_ctx_t *ctx, pgp_source_t *src, pgp_dest_t *dst)
                       ctx->dump_mpi);
         break;
     case PGP_PKA_SPHINCSPLUS_SHA2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHAKE:
         dst_print_vec(dst,
                       "sphincs+ encoded pubkey",
@@ -1161,14 +1161,14 @@ stream_dump_pk_session_key(rnp_dump_ctx_t *ctx, pgp_source_t *src, pgp_dest_t *d
 #endif
 #if defined(ENABLE_PQC)
     case PGP_PKA_KYBER768_X25519:
-        [[fallthrough]];
-    // TODO add case PGP_PKA_KYBER1024_X448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO add case PGP_PKA_KYBER1024_X448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_BP384:
         dst_print_vec(dst,
                       "kyber-ecdh composite ciphertext",
@@ -1988,19 +1988,19 @@ stream_dump_signature_pkt_json(rnp_dump_ctx_t *       ctx,
 #endif
 #if defined(ENABLE_PQC)
     case PGP_PKA_DILITHIUM3_ED25519:
-        [[fallthrough]];
-    // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_BP384:
         /* TODO */
         break;
     case PGP_PKA_SPHINCSPLUS_SHA2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHAKE:
         /* TODO */
         break;
@@ -2126,31 +2126,31 @@ stream_dump_key_json(rnp_dump_ctx_t *ctx, pgp_source_t *src, json_object *pkt)
 #endif
 #if defined(ENABLE_PQC)
     case PGP_PKA_KYBER768_X25519:
-        [[fallthrough]];
-    // TODO add case PGP_PKA_KYBER1024_X448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO add case PGP_PKA_KYBER1024_X448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_BP384:
         // TODO
         break;
     case PGP_PKA_DILITHIUM3_ED25519:
-        [[fallthrough]];
-    // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_BP384:
         /* TODO */
         break;
     case PGP_PKA_SPHINCSPLUS_SHA2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHAKE:
         /* TODO */
         break;
@@ -2292,14 +2292,14 @@ stream_dump_pk_session_key_json(rnp_dump_ctx_t *ctx, pgp_source_t *src, json_obj
 #endif
 #if defined(ENABLE_PQC)
     case PGP_PKA_KYBER768_X25519:
-        [[fallthrough]];
-    // TODO add case PGP_PKA_KYBER1024_X448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO add case PGP_PKA_KYBER1024_X448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_BP384:
         // TODO
         break;
diff --git a/src/librepgp/stream-key.cpp b/src/librepgp/stream-key.cpp
index ac95d548..c3b180bb 100644
--- a/src/librepgp/stream-key.cpp
+++ b/src/librepgp/stream-key.cpp
@@ -545,7 +545,7 @@ parse_secret_key_mpis(pgp_key_pkt_t &key, const uint8_t *mpis, size_t len)
         if (key.version == PGP_V6) {
             break; /* checksum removed for v6 and usage byte zero */
         }
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
 #endif
     case PGP_S2KU_ENCRYPTED: {
         /* calculate and check sum16 of the cleartext */
@@ -658,14 +658,14 @@ parse_secret_key_mpis(pgp_key_pkt_t &key, const uint8_t *mpis, size_t len)
 #endif
 #if defined(ENABLE_PQC)
         case PGP_PKA_KYBER768_X25519:
-            [[fallthrough]];
-        // TODO add case PGP_PKA_KYBER1024_X448: [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
+        // TODO add case PGP_PKA_KYBER1024_X448: FALLTHROUGH_STATEMENT;
         case PGP_PKA_KYBER768_P256:
-            [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
         case PGP_PKA_KYBER1024_P384:
-            [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
         case PGP_PKA_KYBER768_BP256:
-            [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
         case PGP_PKA_KYBER1024_BP384:
             tmpbuf.resize(pgp_kyber_ecdh_composite_private_key_t::encoded_size(key.alg));
             if (!body.get(tmpbuf.data(), tmpbuf.size())) {
@@ -676,14 +676,14 @@ parse_secret_key_mpis(pgp_key_pkt_t &key, const uint8_t *mpis, size_t len)
               pgp_kyber_ecdh_composite_private_key_t(tmpbuf.data(), tmpbuf.size(), key.alg);
             break;
         case PGP_PKA_DILITHIUM3_ED25519:
-            [[fallthrough]];
-        // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
+        // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
         case PGP_PKA_DILITHIUM3_P256:
-            [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
         case PGP_PKA_DILITHIUM5_P384:
-            [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
         case PGP_PKA_DILITHIUM3_BP256:
-            [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
         case PGP_PKA_DILITHIUM5_BP384:
             tmpbuf.resize(pgp_dilithium_exdsa_composite_private_key_t::encoded_size(key.alg));
             if (!body.get(tmpbuf.data(), tmpbuf.size())) {
@@ -694,7 +694,7 @@ parse_secret_key_mpis(pgp_key_pkt_t &key, const uint8_t *mpis, size_t len)
               tmpbuf.data(), tmpbuf.size(), key.alg);
             break;
         case PGP_PKA_SPHINCSPLUS_SHA2:
-            [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
         case PGP_PKA_SPHINCSPLUS_SHAKE: {
             uint8_t param;
             if (!body.get(param)) {
@@ -844,31 +844,31 @@ write_secret_key_mpis(pgp_packet_body_t &body, pgp_key_pkt_t &key)
 #endif
 #if defined(ENABLE_PQC)
     case PGP_PKA_KYBER768_X25519:
-        [[fallthrough]];
-    // TODO add case PGP_PKA_KYBER1024_X448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO add case PGP_PKA_KYBER1024_X448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_BP384:
         body.add(key.material.kyber_ecdh.priv.get_encoded());
         break;
     case PGP_PKA_DILITHIUM3_ED25519:
-        [[fallthrough]];
-    // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_BP384:
         body.add(key.material.dilithium_exdsa.priv.get_encoded());
         break;
     case PGP_PKA_SPHINCSPLUS_SHA2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHAKE:
         body.add_byte((uint8_t) key.material.sphincsplus.priv.param());
         body.add(key.material.sphincsplus.priv.get_encoded());
@@ -1029,28 +1029,28 @@ forget_secret_key_fields(pgp_key_material_t *key)
 #endif
 #if defined(ENABLE_PQC)
     case PGP_PKA_KYBER768_X25519:
-        [[fallthrough]];
-    // TODO add case PGP_PKA_KYBER1024_X448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO add case PGP_PKA_KYBER1024_X448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_ED25519:
-        [[fallthrough]];
-    // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_BP384:
         key->dilithium_exdsa.priv.secure_clear();
         break;
     case PGP_PKA_SPHINCSPLUS_SHA2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHAKE:
         key->sphincsplus.priv.secure_clear();
         break;
@@ -1403,9 +1403,9 @@ pgp_key_pkt_t::parse(pgp_source_t &src)
     }
     switch (ver) {
     case PGP_V2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_V3:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_V4:
         break;
 #if defined(ENABLE_CRYPTO_REFRESH)
@@ -1517,14 +1517,14 @@ pgp_key_pkt_t::parse(pgp_source_t &src)
 #endif
 #if defined(ENABLE_PQC)
     case PGP_PKA_KYBER768_X25519:
-        [[fallthrough]];
-    // TODO add case PGP_PKA_KYBER1024_X448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO add case PGP_PKA_KYBER1024_X448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_BP384:
         tmpbuf.resize(pgp_kyber_ecdh_composite_public_key_t::encoded_size(alg));
         if (!pkt.get(tmpbuf.data(), tmpbuf.size())) {
@@ -1534,14 +1534,14 @@ pgp_key_pkt_t::parse(pgp_source_t &src)
         material.kyber_ecdh.pub = pgp_kyber_ecdh_composite_public_key_t(tmpbuf, alg);
         break;
     case PGP_PKA_DILITHIUM3_ED25519:
-        [[fallthrough]];
-    // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_BP384:
         tmpbuf.resize(pgp_dilithium_exdsa_composite_public_key_t::encoded_size(alg));
         if (!pkt.get(tmpbuf.data(), tmpbuf.size())) {
@@ -1551,7 +1551,7 @@ pgp_key_pkt_t::parse(pgp_source_t &src)
         material.dilithium_exdsa.pub = pgp_dilithium_exdsa_composite_public_key_t(tmpbuf, alg);
         break;
     case PGP_PKA_SPHINCSPLUS_SHA2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHAKE: {
         uint8_t param;
         if (!pkt.get(param)) {
@@ -1717,31 +1717,31 @@ pgp_key_pkt_t::make_alg_spec_fields_for_public_key(pgp_packet_body_t &hbody)
 #endif
 #if defined(ENABLE_PQC)
     case PGP_PKA_KYBER768_X25519:
-        [[fallthrough]];
-    // TODO add case PGP_PKA_KYBER1024_X448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO add case PGP_PKA_KYBER1024_X448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_BP384:
         hbody.add(material.kyber_ecdh.pub.get_encoded());
         break;
     case PGP_PKA_DILITHIUM3_ED25519:
-        [[fallthrough]];
-    // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_BP384:
         hbody.add(material.dilithium_exdsa.pub.get_encoded());
         break;
     case PGP_PKA_SPHINCSPLUS_SHA2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHAKE:
         hbody.add_byte((uint8_t) material.sphincsplus.pub.param());
         hbody.add(material.sphincsplus.pub.get_encoded());
diff --git a/src/librepgp/stream-packet.cpp b/src/librepgp/stream-packet.cpp
index b547ff01..7342a326 100644
--- a/src/librepgp/stream-packet.cpp
+++ b/src/librepgp/stream-packet.cpp
@@ -1243,14 +1243,14 @@ pgp_pk_sesskey_t::parse_material(pgp_encrypted_material_t &material) const
 #endif
 #if defined(ENABLE_PQC)
     case PGP_PKA_KYBER768_X25519:
-        [[fallthrough]];
-    // TODO add case PGP_PKA_KYBER1024_X448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO add case PGP_PKA_KYBER1024_X448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_BP384: {
         uint8_t wrapped_key_len = 0;
         material.kyber_ecdh.composite_ciphertext.resize(
@@ -1316,14 +1316,14 @@ pgp_pk_sesskey_t::write_material(const pgp_encrypted_material_t &material)
 #endif
 #if defined(ENABLE_PQC)
     case PGP_PKA_KYBER768_X25519:
-        [[fallthrough]];
-    // TODO add case PGP_PKA_KYBER1024_X448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO add case PGP_PKA_KYBER1024_X448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_BP384:
         pktbody.add(material.kyber_ecdh.composite_ciphertext);
         pktbody.add_byte(static_cast<uint8_t>(material.kyber_ecdh.wrapped_sesskey.size()));
diff --git a/src/librepgp/stream-parse.cpp b/src/librepgp/stream-parse.cpp
index 4b924bc2..aed70530 100644
--- a/src/librepgp/stream-parse.cpp
+++ b/src/librepgp/stream-parse.cpp
@@ -1504,15 +1504,15 @@ do_enforce_aes_v3pkesk(pgp_pubkey_alg_t alg)
     switch (alg) {
 #if defined(ENABLE_PQC)
     case PGP_PKA_KYBER768_X25519:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_BP384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
 #endif
     case PGP_PKA_X25519:
         return true;
@@ -1644,14 +1644,14 @@ encrypted_try_key(pgp_source_encrypted_param_t *param,
 #endif
 #if defined(ENABLE_PQC)
     case PGP_PKA_KYBER768_X25519:
-        [[fallthrough]];
-    // TODO add case PGP_PKA_KYBER1024_X448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO add case PGP_PKA_KYBER1024_X448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_BP384: {
         pgp_key_t key(*seckey, true); /* make public-key `pgp_key_t` object from seckey */
         declen = decbuf.size();
diff --git a/src/librepgp/stream-sig.cpp b/src/librepgp/stream-sig.cpp
index 684e3104..c256ef46 100644
--- a/src/librepgp/stream-sig.cpp
+++ b/src/librepgp/stream-sig.cpp
@@ -50,9 +50,9 @@ signature_hash_key(const pgp_key_pkt_t &key, rnp::Hash &hash)
 {
     switch (key.version) {
     case PGP_V2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_V3:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_V4: {
         uint8_t hdr[3] = {0x99, 0x00, 0x00};
         if (key.hashed_data) {
@@ -1443,13 +1443,13 @@ pgp_signature_t::parse(pgp_packet_body_t &pkt)
     rnp_result_t res;
     switch (ver) {
     case PGP_V2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_V3:
         res = parse_v2v3(pkt);
         break;
 #if defined(ENABLE_CRYPTO_REFRESH)
     case PGP_V6:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
 #endif
     case PGP_V4:
         res = parse_v4up(pkt);
@@ -1539,9 +1539,7 @@ pgp_signature_t::parse_material(pgp_signature_material_t &material) const
         if (version < PGP_V4) {
             RNP_LOG("Warning! v3 EdDSA signature.");
         }
-#if (!defined(_MSVC_LANG) || _MSVC_LANG >= 201703L)
-        [[fallthrough]];
-#endif
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_ECDSA:
     case PGP_PKA_SM2:
     case PGP_PKA_ECDH:
@@ -1568,14 +1566,14 @@ pgp_signature_t::parse_material(pgp_signature_material_t &material) const
 #endif
 #if defined(ENABLE_PQC)
     case PGP_PKA_DILITHIUM3_ED25519:
-        [[fallthrough]];
-    // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_BP384:
         material.dilithium_exdsa.sig.resize(
           pgp_dilithium_exdsa_signature_t::composite_signature_size(palg));
@@ -1586,7 +1584,7 @@ pgp_signature_t::parse_material(pgp_signature_material_t &material) const
         }
         break;
     case PGP_PKA_SPHINCSPLUS_SHA2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHAKE: {
         uint8_t param;
         if (!pkt.get(param)) {
@@ -1620,9 +1618,9 @@ pgp_signature_t::write(pgp_dest_t &dst) const
 {
     switch (version) {
     case PGP_V2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_V3:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_V4:
         break;
 #if defined(ENABLE_CRYPTO_REFRESH)
@@ -1693,19 +1691,19 @@ pgp_signature_t::write_material(const pgp_signature_material_t &material)
 #endif
 #if defined(ENABLE_PQC)
     case PGP_PKA_DILITHIUM3_ED25519:
-        [[fallthrough]];
-    // TODO: add case PGP_PKA_DILITHIUM5_ED448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO: add case PGP_PKA_DILITHIUM5_ED448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM3_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_DILITHIUM5_BP384:
         pktbody.add(material.dilithium_exdsa.sig);
         break;
     case PGP_PKA_SPHINCSPLUS_SHA2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_SPHINCSPLUS_SHAKE:
         pktbody.add_byte((uint8_t) material.sphincsplus.param);
         pktbody.add(material.sphincsplus.sig);
@@ -1731,9 +1729,9 @@ pgp_signature_t::fill_hashed_data()
     /* we don't have a need to write v2-v3 signatures */
     switch (version) {
     case PGP_V2:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_V3:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_V4:
         break;
 #if defined(ENABLE_CRYPTO_REFRESH)
diff --git a/src/librepgp/stream-write.cpp b/src/librepgp/stream-write.cpp
index 9223681f..acf122f9 100644
--- a/src/librepgp/stream-write.cpp
+++ b/src/librepgp/stream-write.cpp
@@ -722,14 +722,14 @@ encrypted_add_recipient(pgp_write_handler_t *handler,
 #endif
 #if defined(ENABLE_PQC)
     case PGP_PKA_KYBER768_X25519:
-        [[fallthrough]];
-    // TODO add case PGP_PKA_KYBER1024_X448: [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
+    // TODO add case PGP_PKA_KYBER1024_X448: FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_P256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_P384:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER768_BP256:
-        [[fallthrough]];
+        FALLTHROUGH_STATEMENT;
     case PGP_PKA_KYBER1024_BP384:
         ret = userkey->material().kyber_ecdh.pub.encrypt(
           &handler->ctx->ctx->rng, &material.kyber_ecdh, enckey.data(), enckey_len);
diff --git a/src/rnp/rnp.cpp b/src/rnp/rnp.cpp
index 3dfcad85..a4b41f1e 100644
--- a/src/rnp/rnp.cpp
+++ b/src/rnp/rnp.cpp
@@ -307,9 +307,7 @@ setcmd(rnp_cfg &cfg, int cmd, const char *arg)
         break;
     case CMD_CLEARSIGN:
         cfg.set_bool(CFG_CLEARTEXT, true);
-#if (!defined(_MSVC_LANG) || _MSVC_LANG >= 201703L)
-        [[fallthrough]];
-#endif
+        FALLTHROUGH_STATEMENT;
     case CMD_SIGN:
         cfg.set_bool(CFG_NEEDSSECKEY, true);
         cfg.set_bool(CFG_SIGN_NEEDED, true);
@@ -326,9 +324,7 @@ setcmd(rnp_cfg &cfg, int cmd, const char *arg)
     case CMD_VERIFY:
         /* single verify will discard output, decrypt will not */
         cfg.set_bool(CFG_NO_OUTPUT, true);
-#if (!defined(_MSVC_LANG) || _MSVC_LANG >= 201703L)
-        [[fallthrough]];
-#endif
+        FALLTHROUGH_STATEMENT;
     case CMD_VERIFY_CAT:
         newcmd = CMD_PROCESS;
         break;
@@ -607,9 +603,7 @@ set_short_option(rnp_cfg &cfg, int ch, const char *arg)
         cfg.set_bool(CFG_KEYSTORE_DISABLED, true);
         break;
     case 'h':
-#if (!defined(_MSVC_LANG) || _MSVC_LANG >= 201703L)
-        [[fallthrough]];
-#endif
+        FALLTHROUGH_STATEMENT;
     default:
         return setcmd(cfg, CMD_HELP, optarg);
     }
diff --git a/src/rnpkeys/main.cpp b/src/rnpkeys/main.cpp
index 3dd088cc..75e3efe5 100644
--- a/src/rnpkeys/main.cpp
+++ b/src/rnpkeys/main.cpp
@@ -52,9 +52,7 @@ get_short_cmd(int ch)
     case 'l':
         return CMD_LIST_KEYS;
     case 'h':
-#if (!defined(_MSVC_LANG) || _MSVC_LANG >= 201703L)
-        [[fallthrough]];
-#endif
+        FALLTHROUGH_STATEMENT;
     default:
         return CMD_HELP;
     }
diff --git a/src/rnpkeys/tui.cpp b/src/rnpkeys/tui.cpp
index 52e9e693..cd9724a7 100644
--- a/src/rnpkeys/tui.cpp
+++ b/src/rnpkeys/tui.cpp
@@ -311,7 +311,7 @@ rnpkeys_ask_generate_params(rnp_cfg &cfg, FILE *input_fp)
 #if defined(ENABLE_CRYPTO_REFRESH)
         case 21: {
             cfg.set_str(CFG_KG_V6_KEY, "true");
-            [[fallthrough]];
+            FALLTHROUGH_STATEMENT;
         }
 #endif
         case 22: {