diff --git a/tools/clang/lib/SPIRV/DeclResultIdMapper.h b/tools/clang/lib/SPIRV/DeclResultIdMapper.h
index 3d9b8450c8..e1a1554124 100644
--- a/tools/clang/lib/SPIRV/DeclResultIdMapper.h
+++ b/tools/clang/lib/SPIRV/DeclResultIdMapper.h
@@ -1146,8 +1146,7 @@ bool DeclResultIdMapper::decorateStageIOLocations() {
 }
 
 bool DeclResultIdMapper::isInputStorageClass(const StageVar &v) {
-  return getStorageClassForSigPoint(v.getSigPoint()) ==
-         spv::StorageClass::Input;
+  return v.getStorageClass() == spv::StorageClass::Input;
 }
 
 void DeclResultIdMapper::createFnParamCounterVar(const VarDecl *param) {
diff --git a/tools/clang/test/CodeGenSPIRV/ext_builtin_input.lib.hlsl b/tools/clang/test/CodeGenSPIRV/ext_builtin_input.lib.hlsl
new file mode 100644
index 0000000000..ce467a0941
--- /dev/null
+++ b/tools/clang/test/CodeGenSPIRV/ext_builtin_input.lib.hlsl
@@ -0,0 +1,16 @@
+// RUN: %dxc -spirv -enable-16bit-types -T lib_6_7 -HV 202x %s | FileCheck %s
+
+// CHECK: OpEntryPoint Fragment %psmain "psmain" %gl_HelperInvocation %out_var_SV_Target0
+// CHECK: OpDecorate %gl_HelperInvocation BuiltIn HelperInvocation
+// CHECK: %gl_HelperInvocation = OpVariable %_ptr_Input_bool Input
+
+[[vk::ext_builtin_input(23 /* BuiltInHelperInvocation */)]]
+static const bool HelperInvocation;
+
+[shader("pixel")]
+float4 psmain() : SV_Target0 {
+
+    if (HelperInvocation)
+      return 0;
+    return 1;
+}