diff --git a/reference/opt/shaders-msl/frag/helper-invocation.msl21.frag b/reference/opt/shaders-msl/frag/helper-invocation.msl21.frag
index a833fa08..9d876df1 100644
--- a/reference/opt/shaders-msl/frag/helper-invocation.msl21.frag
+++ b/reference/opt/shaders-msl/frag/helper-invocation.msl21.frag
@@ -16,9 +16,8 @@ struct main0_in
 fragment main0_out main0(main0_in in [[stage_in]], texture2d<float> uSampler [[texture(0)]], sampler uSamplerSmplr [[sampler(0)]])
 {
     main0_out out = {};
-    bool gl_HelperInvocation = simd_is_helper_thread();
     float4 _52;
-    if (!gl_HelperInvocation)
+    if (!simd_is_helper_thread())
     {
         _52 = uSampler.sample(uSamplerSmplr, in.vUV, level(0.0));
     }
diff --git a/reference/shaders-msl-no-opt/frag/volatile-helper-invocation.msl23.spv16.frag b/reference/shaders-msl-no-opt/frag/volatile-helper-invocation.msl23.spv16.frag
index 562cddaa..eef92efe 100644
--- a/reference/shaders-msl-no-opt/frag/volatile-helper-invocation.msl23.spv16.frag
+++ b/reference/shaders-msl-no-opt/frag/volatile-helper-invocation.msl23.spv16.frag
@@ -11,12 +11,11 @@ struct main0_out
 fragment main0_out main0()
 {
     main0_out out = {};
-    bool gl_HelperInvocation = simd_is_helper_thread();
-    bool _12 = gl_HelperInvocation;
+    bool _12 = simd_is_helper_thread();
     float _15 = float(_12);
     out.FragColor = _15;
     discard_fragment();
-    bool _16 = gl_HelperInvocation;
+    bool _16 = simd_is_helper_thread();
     float _17 = float(_16);
     out.FragColor = _17;
     return out;
diff --git a/reference/shaders-msl/frag/helper-invocation.msl21.frag b/reference/shaders-msl/frag/helper-invocation.msl21.frag
index 7cf97a25..36d14239 100644
--- a/reference/shaders-msl/frag/helper-invocation.msl21.frag
+++ b/reference/shaders-msl/frag/helper-invocation.msl21.frag
@@ -16,10 +16,10 @@ struct main0_in
 };
 
 static inline __attribute__((always_inline))
-float4 foo(thread bool& gl_HelperInvocation, texture2d<float> uSampler, sampler uSamplerSmplr, thread float2& vUV)
+float4 foo(texture2d<float> uSampler, sampler uSamplerSmplr, thread float2& vUV)
 {
     float4 color;
-    if (!gl_HelperInvocation)
+    if (!simd_is_helper_thread())
     {
         color = uSampler.sample(uSamplerSmplr, vUV, level(0.0));
     }
@@ -33,8 +33,7 @@ float4 foo(thread bool& gl_HelperInvocation, texture2d<float> uSampler, sampler
 fragment main0_out main0(main0_in in [[stage_in]], texture2d<float> uSampler [[texture(0)]], sampler uSamplerSmplr [[sampler(0)]])
 {
     main0_out out = {};
-    bool gl_HelperInvocation = simd_is_helper_thread();
-    out.FragColor = foo(gl_HelperInvocation, uSampler, uSamplerSmplr, in.vUV);
+    out.FragColor = foo(uSampler, uSamplerSmplr, in.vUV);
     return out;
 }
 
diff --git a/spirv_msl.cpp b/spirv_msl.cpp
index 4eeb3b7f..8ea27d5f 100644
--- a/spirv_msl.cpp
+++ b/spirv_msl.cpp
@@ -1548,6 +1548,14 @@ void CompilerMSL::extract_global_variables_from_functions()
 	// Uniforms
 	unordered_set<uint32_t> global_var_ids;
 	ir.for_each_typed_id<SPIRVariable>([&](uint32_t, SPIRVariable &var) {
+		// Some builtins resolve directly to a function call which does not need any declared variables.
+		// Skip these.
+		if (var.storage == StorageClassInput && has_decoration(var.self, DecorationBuiltIn) &&
+		    BuiltIn(get_decoration(var.self, DecorationBuiltIn)) == BuiltInHelperInvocation)
+		{
+			return;
+		}
+
 		if (var.storage == StorageClassInput || var.storage == StorageClassOutput ||
 		    var.storage == StorageClassUniform || var.storage == StorageClassUniformConstant ||
 		    var.storage == StorageClassPushConstant || var.storage == StorageClassStorageBuffer)
@@ -12163,16 +12171,6 @@ void CompilerMSL::fix_up_shader_inputs_outputs()
 					});
 				}
 				break;
-			case BuiltInHelperInvocation:
-				if (msl_options.is_ios() && !msl_options.supports_msl_version(2, 3))
-					SPIRV_CROSS_THROW("simd_is_helper_thread() requires version 2.3 on iOS.");
-				else if (msl_options.is_macos() && !msl_options.supports_msl_version(2, 1))
-					SPIRV_CROSS_THROW("simd_is_helper_thread() requires version 2.1 on macOS.");
-
-				entry_func.fixup_hooks_in.push_back([=]() {
-					statement(builtin_type_decl(bi_type), " ", to_expression(var_id), " = simd_is_helper_thread();");
-				});
-				break;
 			case BuiltInInvocationId:
 				// This is direct-mapped without multi-patch workgroups.
 				if (get_execution_model() != ExecutionModelTessellationControl || !msl_options.multi_patch_workgroup)
@@ -14467,6 +14465,14 @@ string CompilerMSL::builtin_to_glsl(BuiltIn builtin, StorageClass storage)
 		}
 		break;
 
+	case BuiltInHelperInvocation:
+		if (msl_options.is_ios() && !msl_options.supports_msl_version(2, 3))
+			SPIRV_CROSS_THROW("simd_is_helper_thread() requires version 2.3 on iOS.");
+		else if (msl_options.is_macos() && !msl_options.supports_msl_version(2, 1))
+			SPIRV_CROSS_THROW("simd_is_helper_thread() requires version 2.1 on macOS.");
+		// In SPIR-V 1.6 with Volatile HelperInvocation, we cannot emit a fixup early.
+		return "simd_is_helper_thread()";
+
 	default:
 		break;
 	}