diff --git a/common/util/gltf_util.cpp b/common/util/gltf_util.cpp
index 22af8f2664a..f9e549d0c53 100644
--- a/common/util/gltf_util.cpp
+++ b/common/util/gltf_util.cpp
@@ -680,6 +680,28 @@ EnvmapSettings envmap_settings_from_gltf(const tinygltf::Material& mat) {
   return settings;
 }
 
+bool material_has_envmap(const tinygltf::Material& mat) {
+  return mat.extensions.contains("KHR_materials_specular");
+}
+
+bool envmap_is_valid(const tinygltf::Material& mat, bool die) {
+  if (material_has_envmap(mat) && mat.pbrMetallicRoughness.metallicRoughnessTexture.index < 0) {
+    std::string error = fmt::format(
+        "Material \"{}\" has specular property set, but is missing a metallic roughness texture! "
+        "Check "
+        "that the Specular IOR level for the material is at the default of 0.5 if this is "
+        "unintended.",
+        mat.name);
+    if (die) {
+      lg::die(error);
+    } else {
+      lg::error(error);
+    }
+    return false;
+  }
+  return true;
+}
+
 std::optional<int> find_single_skin(const tinygltf::Model& model,
                                     const std::vector<NodeWithTransform>& all_nodes) {
   std::optional<int> skin_index;
diff --git a/common/util/gltf_util.h b/common/util/gltf_util.h
index 627110cb751..01cfbce1245 100644
--- a/common/util/gltf_util.h
+++ b/common/util/gltf_util.h
@@ -125,6 +125,8 @@ struct EnvmapSettings {
 };
 
 EnvmapSettings envmap_settings_from_gltf(const tinygltf::Material& mat);
+bool material_has_envmap(const tinygltf::Material& mat);
+bool envmap_is_valid(const tinygltf::Material& mat, bool die);
 
 /*!
  * Find the index of the skin for this model. Returns nullopt if there is no skin, the index of the
diff --git a/decompiler/level_extractor/merc_replacement.cpp b/decompiler/level_extractor/merc_replacement.cpp
index 2afed37bd1a..c35647e2e31 100644
--- a/decompiler/level_extractor/merc_replacement.cpp
+++ b/decompiler/level_extractor/merc_replacement.cpp
@@ -4,10 +4,6 @@ using namespace gltf_util;
 
 namespace decompiler {
 
-bool material_has_envmap(const tinygltf::Material& mat) {
-  return mat.extensions.contains("KHR_materials_specular");
-}
-
 void extract(const std::string& name,
              MercExtractData& out,
              const tinygltf::Model& model,
@@ -25,7 +21,7 @@ void extract(const std::string& name,
   int joints = 3;
   auto skin_idx = find_single_skin(model, all_nodes);
   if (skin_idx) {
-    joints = get_joint_count(model, *skin_idx);
+    joints += get_joint_count(model, *skin_idx);
   }
 
   for (const auto& n : all_nodes) {
@@ -134,14 +130,13 @@ void extract(const std::string& name,
       return;
     }
 
-    int roughness_tex_idx = mat.pbrMetallicRoughness.metallicRoughnessTexture.index;
-    ASSERT(roughness_tex_idx >= 0);
     const auto& base_tex = model.textures[base_tex_idx];
     ASSERT(base_tex.sampler >= 0);
     ASSERT(base_tex.source >= 0);
     gltf_util::setup_draw_mode_from_sampler(model.samplers.at(base_tex.sampler), &draw.mode);
     gltf_util::setup_alpha_from_material(mat, &draw.mode);
-    const auto& roughness_tex = model.textures.at(roughness_tex_idx);
+    const auto& roughness_tex =
+        model.textures.at(mat.pbrMetallicRoughness.metallicRoughnessTexture.index);
     ASSERT(roughness_tex.sampler >= 0);
     ASSERT(roughness_tex.source >= 0);
 
@@ -169,6 +164,7 @@ void extract(const std::string& name,
     if (!material_has_envmap(mat)) {
       process_normal_draw(e, mat_idx, d_);
     } else {
+      envmap_is_valid(mat, true);
       has_envmaps = true;
       envmap_eff.has_envmap = true;
       process_envmap_draw(envmap_eff, mat_idx, d_);
diff --git a/goalc/build_actor/common/MercExtract.cpp b/goalc/build_actor/common/MercExtract.cpp
index fb857b8dc23..db20ea69516 100644
--- a/goalc/build_actor/common/MercExtract.cpp
+++ b/goalc/build_actor/common/MercExtract.cpp
@@ -5,10 +5,6 @@
 
 #include "goalc/build_level/common/gltf_mesh_extract.h"
 
-bool material_has_envmap(const tinygltf::Material& mat) {
-  return mat.extensions.contains("KHR_materials_specular");
-}
-
 void extract(const std::string& name,
              MercExtractData& out,
              const tinygltf::Model& model,
@@ -25,7 +21,7 @@ void extract(const std::string& name,
   int joints = 3;
   auto skin_idx = find_single_skin(model, all_nodes);
   if (skin_idx) {
-    joints = gltf_util::get_joint_count(model, *skin_idx);
+    joints += gltf_util::get_joint_count(model, *skin_idx);
   }
 
   for (const auto& n : all_nodes) {
@@ -146,14 +142,13 @@ void extract(const std::string& name,
       return;
     }
 
-    int roughness_tex_idx = mat.pbrMetallicRoughness.metallicRoughnessTexture.index;
-    ASSERT(roughness_tex_idx >= 0);
     const auto& base_tex = model.textures[base_tex_idx];
     ASSERT(base_tex.sampler >= 0);
     ASSERT(base_tex.source >= 0);
     gltf_util::setup_draw_mode_from_sampler(model.samplers.at(base_tex.sampler), &draw.mode);
     gltf_util::setup_alpha_from_material(mat, &draw.mode);
-    const auto& roughness_tex = model.textures.at(roughness_tex_idx);
+    const auto& roughness_tex =
+        model.textures.at(mat.pbrMetallicRoughness.metallicRoughnessTexture.index);
     ASSERT(roughness_tex.sampler >= 0);
     ASSERT(roughness_tex.source >= 0);
 
@@ -178,9 +173,10 @@ void extract(const std::string& name,
 
   for (const auto& [mat_idx, d_] : draw_by_material) {
     const auto& mat = model.materials[mat_idx];
-    if (!material_has_envmap(mat)) {
+    if (!gltf_util::material_has_envmap(mat)) {
       process_normal_draw(e, mat_idx, d_);
     } else {
+      gltf_util::envmap_is_valid(mat, false);
       has_envmaps = true;
       envmap_eff.has_envmap = true;
       process_envmap_draw(envmap_eff, mat_idx, d_);