diff --git a/Source/Core/VideoCommon/GeometryShaderGen.cpp b/Source/Core/VideoCommon/GeometryShaderGen.cpp
index de76557d5e..4d551f5d16 100644
--- a/Source/Core/VideoCommon/GeometryShaderGen.cpp
+++ b/Source/Core/VideoCommon/GeometryShaderGen.cpp
@@ -90,16 +90,15 @@ static T GenerateGeometryShader(u32 primitive_type, API_TYPE ApiType)
 		if (g_ActiveConfig.backend_info.bSupportsGSInstancing)
 			out.Write("#define InstanceID gl_InvocationID\n");
 
-		out.Write("// The interface block qualifier is duplicated to its member due to Apple OS X bug 24983074\n");
 		out.Write("in VertexData {\n");
-		GenerateVSOutputMembers<T>(out, ApiType, "in", GetInterpolationQualifier());
+		GenerateVSOutputMembers<T>(out, ApiType, GetInterpolationQualifier(true, true));
 		out.Write("} vs[%d];\n", vertex_in);
 
 		out.Write("out VertexData {\n");
-		GenerateVSOutputMembers<T>(out, ApiType, "out", GetInterpolationQualifier());
+		GenerateVSOutputMembers<T>(out, ApiType, GetInterpolationQualifier(true, false));
 
 		if (g_ActiveConfig.iStereoMode > 0)
-			out.Write("\tflat out int layer;\n");
+			out.Write("\tflat int layer;\n");
 
 		out.Write("} ps;\n");
 
diff --git a/Source/Core/VideoCommon/PixelShaderGen.cpp b/Source/Core/VideoCommon/PixelShaderGen.cpp
index cc0ab52422..5ae79e0733 100644
--- a/Source/Core/VideoCommon/PixelShaderGen.cpp
+++ b/Source/Core/VideoCommon/PixelShaderGen.cpp
@@ -354,12 +354,11 @@ static T GeneratePixelShader(DSTALPHA_MODE dstAlphaMode, API_TYPE ApiType)
 		uid_data->stereo = g_ActiveConfig.iStereoMode > 0;
 		if (g_ActiveConfig.backend_info.bSupportsGeometryShaders)
 		{
-			out.Write("// The interface block qualifier is duplicated to its member due to Apple OS X bug 24983074\n");
 			out.Write("in VertexData {\n");
-			GenerateVSOutputMembers<T>(out, ApiType, "in", GetInterpolationQualifier());
+			GenerateVSOutputMembers<T>(out, ApiType, GetInterpolationQualifier(true, true));
 
 			if (g_ActiveConfig.iStereoMode > 0)
-				out.Write("\tflat in int layer;\n");
+				out.Write("\tflat int layer;\n");
 
 			out.Write("};\n");
 		}
diff --git a/Source/Core/VideoCommon/ShaderGenCommon.h b/Source/Core/VideoCommon/ShaderGenCommon.h
index 9283cdc8cc..18c40af41e 100644
--- a/Source/Core/VideoCommon/ShaderGenCommon.h
+++ b/Source/Core/VideoCommon/ShaderGenCommon.h
@@ -214,12 +214,9 @@ private:
 };
 
 template<class T>
-inline void DefineOutputMember(T& object, API_TYPE api_type, const char* qualifier, const char* in_out, const char* type, const char* name, int var_index, const char* semantic = "", int semantic_index = -1)
+inline void DefineOutputMember(T& object, API_TYPE api_type, const char* qualifier, const char* type, const char* name, int var_index, const char* semantic = "", int semantic_index = -1)
 {
-	if (qualifier != nullptr)
-		object.Write("\t%s %s %s %s", qualifier, in_out, type, name);
-	else
-		object.Write("\t%s %s %s", in_out, type, name);
+	object.Write("\t%s %s %s", qualifier, type, name);
 
 	if (var_index != -1)
 		object.Write("%d", var_index);
@@ -236,21 +233,21 @@ inline void DefineOutputMember(T& object, API_TYPE api_type, const char* qualifi
 }
 
 template<class T>
-inline void GenerateVSOutputMembers(T& object, API_TYPE api_type, const char* in_out, const char* qualifier = nullptr)
+inline void GenerateVSOutputMembers(T& object, API_TYPE api_type, const char* qualifier)
 {
-	DefineOutputMember(object, api_type, qualifier, in_out, "float4", "pos", -1, "POSITION");
-	DefineOutputMember(object, api_type, qualifier, in_out, "float4", "colors_", 0, "COLOR", 0);
-	DefineOutputMember(object, api_type, qualifier, in_out, "float4", "colors_", 1, "COLOR", 1);
+	DefineOutputMember(object, api_type, qualifier, "float4", "pos", -1, "POSITION");
+	DefineOutputMember(object, api_type, qualifier, "float4", "colors_", 0, "COLOR", 0);
+	DefineOutputMember(object, api_type, qualifier, "float4", "colors_", 1, "COLOR", 1);
 
 	for (unsigned int i = 0; i < xfmem.numTexGen.numTexGens; ++i)
-		DefineOutputMember(object, api_type, qualifier, in_out, "float3", "tex", i, "TEXCOORD", i);
+		DefineOutputMember(object, api_type, qualifier, "float3", "tex", i, "TEXCOORD", i);
 
-	DefineOutputMember(object, api_type, qualifier, in_out, "float4", "clipPos", -1, "TEXCOORD", xfmem.numTexGen.numTexGens);
+	DefineOutputMember(object, api_type, qualifier, "float4", "clipPos", -1, "TEXCOORD", xfmem.numTexGen.numTexGens);
 
 	if (g_ActiveConfig.bEnablePixelLighting)
 	{
-		DefineOutputMember(object, api_type, qualifier, in_out, "float3", "Normal", -1, "TEXCOORD", xfmem.numTexGen.numTexGens + 1);
-		DefineOutputMember(object, api_type, qualifier, in_out, "float3", "WorldPos", -1, "TEXCOORD", xfmem.numTexGen.numTexGens + 2);
+		DefineOutputMember(object, api_type, qualifier, "float3", "Normal", -1, "TEXCOORD", xfmem.numTexGen.numTexGens + 1);
+		DefineOutputMember(object, api_type, qualifier, "float3", "WorldPos", -1, "TEXCOORD", xfmem.numTexGen.numTexGens + 2);
 	}
 }
 
@@ -281,15 +278,27 @@ inline void AssignVSOutputMembers(T& object, const char* a, const char* b)
 // As a workaround, we interpolate at the centroid of the coveraged pixel, which
 // is always inside the primitive.
 // Without MSAA, this flag is defined to have no effect.
-inline const char* GetInterpolationQualifier()
+inline const char* GetInterpolationQualifier(bool in_glsl_interface_block = false, bool in = false)
 {
 	if (g_ActiveConfig.iMultisamples <= 1)
 		return "";
 
-	if (!g_ActiveConfig.bSSAA)
-		return "centroid";
-
-	return "sample";
+	// Without GL_ARB_shading_language_420pack support, the interpolation qualifier must be
+	// "centroid in" and not "centroid", even within an interface block.
+	if (in_glsl_interface_block && !g_ActiveConfig.backend_info.bSupportsBindingLayout)
+	{
+		if (!g_ActiveConfig.bSSAA)
+			return in ? "centroid in" : "centroid out";
+		else
+			return in ? "sample in" : "sample out";
+	}
+	else
+	{
+		if (!g_ActiveConfig.bSSAA)
+			return "centroid";
+		else
+			return "sample";
+	}
 }
 
 // Constant variable names
diff --git a/Source/Core/VideoCommon/VertexShaderGen.cpp b/Source/Core/VideoCommon/VertexShaderGen.cpp
index 1b436bf852..5a31a6e16c 100644
--- a/Source/Core/VideoCommon/VertexShaderGen.cpp
+++ b/Source/Core/VideoCommon/VertexShaderGen.cpp
@@ -74,9 +74,8 @@ static T GenerateVertexShader(API_TYPE api_type)
 
 		if (g_ActiveConfig.backend_info.bSupportsGeometryShaders)
 		{
-			out.Write("// The interface block qualifier is duplicated to its member due to Apple OS X bug 24983074\n");
 			out.Write("out VertexData {\n");
-			GenerateVSOutputMembers<T>(out, api_type, "out", GetInterpolationQualifier());
+			GenerateVSOutputMembers<T>(out, api_type, GetInterpolationQualifier(true, false));
 			out.Write("} vs;\n");
 		}
 		else