diff --git a/src/libANGLE/renderer/d3d/ProgramExecutableD3D.cpp b/src/libANGLE/renderer/d3d/ProgramExecutableD3D.cpp
index 5d545a61bf..1a23e849db 100644
--- a/src/libANGLE/renderer/d3d/ProgramExecutableD3D.cpp
+++ b/src/libANGLE/renderer/d3d/ProgramExecutableD3D.cpp
@@ -1809,6 +1809,18 @@ void ProgramExecutableD3D::defineUniformBase(gl::ShaderType shaderType,
     }
 
     const SharedCompiledShaderStateD3D &shaderD3D = mAttachedShaders[shaderType];
+    if (!shaderD3D->hasUniform(uniform.name))
+    {
+        // The translator can mark a uniform active (CollectVariables) and then
+        // drop its only reference in a later HLSL-only pass (e.g.
+        // SeparateArrayConstructorStatements), leaving it absent from
+        // uniformRegisterMap.  Mirror the sampler path and skip it instead of
+        // dereferencing end()->second in getUniformRegister().
+        UniformEncodingVisitorD3D visitor(shaderType, HLSLRegisterType::None, &stubEncoder,
+                                          uniformMap);
+        sh::TraverseShaderVariable(uniform, false, &visitor);
+        return;
+    }
     unsigned int startRegister                    = shaderD3D->getUniformRegister(uniform.name);
     ShShaderOutput outputType                     = shaderD3D->compilerOutputType;
     sh::HLSLBlockEncoder encoder(sh::HLSLBlockEncoder::GetStrategyFor(outputType), true);
diff --git a/src/libANGLE/renderer/d3d/ShaderD3D.cpp b/src/libANGLE/renderer/d3d/ShaderD3D.cpp
index 67d573d777..d95597ccfc 100644
--- a/src/libANGLE/renderer/d3d/ShaderD3D.cpp
+++ b/src/libANGLE/renderer/d3d/ShaderD3D.cpp
@@ -230,8 +230,16 @@ void CompiledShaderStateD3D::generateWorkarounds(CompilerWorkaroundsD3D *workaro
 
 unsigned int CompiledShaderStateD3D::getUniformRegister(const std::string &uniformName) const
 {
-    ASSERT(uniformRegisterMap.count(uniformName) > 0);
-    return uniformRegisterMap.find(uniformName)->second;
+    auto it = uniformRegisterMap.find(uniformName);
+    ASSERT(it != uniformRegisterMap.end());
+    if (it == uniformRegisterMap.end())
+    {
+        // Defensive: callers are expected to gate on hasUniform(), but if they
+        // don't, returning GL_INVALID_INDEX keeps isReferencedByShader() false
+        // instead of letting end()->second flow into register-index arithmetic.
+        return GL_INVALID_INDEX;
+    }
+    return it->second;
 }
 
 unsigned int CompiledShaderStateD3D::getUniformBlockRegister(const std::string &blockName) const