diff --git a/p192/src/test_vectors/ecdsa.rs b/p192/src/test_vectors/ecdsa.rs
index 9d2323310..34d37f5ee 100644
--- a/p192/src/test_vectors/ecdsa.rs
+++ b/p192/src/test_vectors/ecdsa.rs
@@ -9,7 +9,7 @@ use hex_literal::hex;
 /// (P-192, SHA-1, from `SigGen.txt` in `186-2ecdsatestvectors.zip`)
 /// <https://csrc.nist.gov/projects/cryptographic-algorithm-validation-program/digital-signatures>
 ///
-/// The `m` field contains a SHA-1 prehash of the `Msg` field in the
+/// The `m` field contains an SHA-1 prehash of the `Msg` field in the
 /// original `SigTen.txt`.
 
 pub const ECDSA_TEST_VECTORS: &[TestVector; 15] = &[
diff --git a/p224/src/test_vectors/ecdsa.rs b/p224/src/test_vectors/ecdsa.rs
index e5810f301..67d22c848 100644
--- a/p224/src/test_vectors/ecdsa.rs
+++ b/p224/src/test_vectors/ecdsa.rs
@@ -9,7 +9,7 @@ use hex_literal::hex;
 /// (P-224, SHA-224, from `SigGen.txt` in `186-4ecdsatestvectors.zip`)
 /// <https://csrc.nist.gov/projects/cryptographic-algorithm-validation-program/digital-signatures>
 ///
-/// The `m` field contains a SHA-224 prehash of the `Msg` field in the
+/// The `m` field contains an SHA-224 prehash of the `Msg` field in the
 /// original `SigTen.txt`.
 
 pub const ECDSA_TEST_VECTORS: &[TestVector; 15] = &[
diff --git a/p384/src/test_vectors/ecdsa.rs b/p384/src/test_vectors/ecdsa.rs
index 2532a8dcb..9b7340d8f 100644
--- a/p384/src/test_vectors/ecdsa.rs
+++ b/p384/src/test_vectors/ecdsa.rs
@@ -9,7 +9,7 @@ use hex_literal::hex;
 /// (P-384, SHA-384, from `SigGen.txt` in `186-4ecdsatestvectors.zip`)
 /// <https://csrc.nist.gov/projects/cryptographic-algorithm-validation-program/digital-signatures>
 ///
-/// The `m` field contains a SHA-384 prehash of the `Msg` field in the
+/// The `m` field contains an SHA-384 prehash of the `Msg` field in the
 /// original `SigTen.txt`.
 pub const ECDSA_TEST_VECTORS: &[TestVector; 15] = &[
     TestVector {
diff --git a/p521/src/test_vectors/ecdsa.rs b/p521/src/test_vectors/ecdsa.rs
index 2894828c9..6151517d9 100644
--- a/p521/src/test_vectors/ecdsa.rs
+++ b/p521/src/test_vectors/ecdsa.rs
@@ -9,7 +9,7 @@ use hex_literal::hex;
 /// (P-521, SHA-521, from `SigGen.txt` in `186-4ecdsatestvectors.zip`)
 /// <https://csrc.nist.gov/projects/cryptographic-algorithm-validation-program/digital-signatures>
 ///
-/// The `m` field contains a SHA-512 prehash of the `Msg` field in the
+/// The `m` field contains an SHA-512 prehash of the `Msg` field in the
 /// original `SigTen.txt`.
 
 pub const ECDSA_TEST_VECTORS: &[TestVector] = &[