diff --git a/renderdoc/driver/gl/gl_shader_refl.cpp b/renderdoc/driver/gl/gl_shader_refl.cpp
index a5a8b6e24..6feaae47f 100644
--- a/renderdoc/driver/gl/gl_shader_refl.cpp
+++ b/renderdoc/driver/gl/gl_shader_refl.cpp
@@ -96,6 +96,69 @@ void copy(rdctype::array<ShaderConstant> &outvars, const vector<DynShaderConstan
 	}
 }
 
+void CheckVertexOutputUses(vector<string> sources, bool &pointSizeUsed, bool &clipDistanceUsed)
+{
+	pointSizeUsed = false;
+	clipDistanceUsed = false;
+
+	for(size_t i=0; i < sources.size(); i++)
+	{
+		string &s = sources[i];
+
+		size_t offs = 0;
+
+		while(true)
+		{
+			offs = s.find("gl_PointSize", offs);
+
+			if(offs == string::npos)
+				break;
+
+			// consider gl_PointSize used if we encounter a '=' before a ';' or the end of the string
+
+			while(offs < s.length())
+			{
+				if(s[offs] == '=')
+				{
+					pointSizeUsed = true;
+					break;
+				}
+
+				if(s[offs] == ';')
+					break;
+
+				offs++;
+			}
+		}
+
+		offs = 0;
+
+		while(true)
+		{
+			offs = s.find("gl_ClipDistance", offs);
+
+			if(offs == string::npos)
+				break;
+
+			// consider gl_ClipDistance used if we encounter a '=' before a ';' or the end of the string
+
+			while(offs < s.length())
+			{
+				if(s[offs] == '=')
+				{
+					clipDistanceUsed = true;
+					break;
+				}
+
+				if(s[offs] == ';')
+					break;
+
+				offs++;
+			}
+		}
+	}
+}
+
 // little utility function that if necessary emulates glCreateShaderProgramv functionality but using glCompileShaderIncludeARB
 static GLuint CreateSepProgram(const GLHookSet &gl, GLenum type, GLsizei numSources, const char **sources, GLsizei numPaths, const char **paths)
 {
@@ -578,7 +641,7 @@ void ReconstructVarTree(const GLHookSet &gl, GLenum query, GLuint sepProg, GLuin
 	}
 }
 
-void MakeShaderReflection(const GLHookSet &gl, GLenum shadType, GLuint sepProg, ShaderReflection &refl)
+void MakeShaderReflection(const GLHookSet &gl, GLenum shadType, GLuint sepProg, ShaderReflection &refl, bool pointSizeUsed, bool clipDistanceUsed)
 {
 	refl.DebugInfo.entryFunc = "main";
 	refl.DebugInfo.compileFlags = 0;
@@ -1424,6 +1487,13 @@ void MakeShaderReflection(const GLHookSet &gl, GLenum shadType, GLuint sepProg,
 
 #define IS_BUILTIN(builtin) !strncmp(nm, builtin, sizeof(builtin)-1)
 
+				// if these weren't used, they were probably added just to make a separable program
+				// (either by us or the program originally). Skip them from the output signature
+				if(IS_BUILTIN("gl_PointSize") && !pointSizeUsed)
+					continue;
+				if(IS_BUILTIN("gl_ClipDistance") && !clipDistanceUsed)
+					continue;
+
 				// VS built-in inputs
 				if(IS_BUILTIN("gl_VertexID"))             sig.systemValue = eAttr_VertexIndex;
 				if(IS_BUILTIN("gl_InstanceID"))           sig.systemValue = eAttr_InstanceIndex;
diff --git a/renderdoc/driver/gl/gl_shader_refl.h b/renderdoc/driver/gl/gl_shader_refl.h
index b9c9a6e21..2c8adcff7 100644
--- a/renderdoc/driver/gl/gl_shader_refl.h
+++ b/renderdoc/driver/gl/gl_shader_refl.h
@@ -26,5 +26,6 @@
 
 #include "replay/replay_driver.h"
 
-void MakeShaderReflection(const GLHookSet &gl, GLenum shadType, GLuint sepProg, ShaderReflection &refl);
+void MakeShaderReflection(const GLHookSet &gl, GLenum shadType, GLuint sepProg, ShaderReflection &refl, bool pointSizeUsed, bool clipDistanceUsed);
 GLuint MakeSeparableShaderProgram(const GLHookSet &gl, GLenum type, std::vector<std::string> sources, vector<string> *includepaths);
+void CheckVertexOutputUses(std::vector<std::string> sources, bool &pointSizeUsed, bool &clipDistanceUsed);
diff --git a/renderdoc/driver/gl/wrappers/gl_shader_funcs.cpp b/renderdoc/driver/gl/wrappers/gl_shader_funcs.cpp
index ba09bcfff..7a308db88 100644
--- a/renderdoc/driver/gl/wrappers/gl_shader_funcs.cpp
+++ b/renderdoc/driver/gl/wrappers/gl_shader_funcs.cpp
@@ -152,6 +152,9 @@ bool WrappedOpenGL::Serialise_glCompileShader(GLuint shader)
 
 		auto &shadDetails = m_Shaders[liveId];
 
+		bool pointSizeUsed = false, clipDistanceUsed = false;
+		if(shadDetails.type == eGL_VERTEX_SHADER) CheckVertexOutputUses(shadDetails.sources, pointSizeUsed, clipDistanceUsed);
+
 		GLuint sepProg = MakeSeparableShaderProgram(m_Real, shadDetails.type, shadDetails.sources, NULL);
 
 		if(sepProg == 0)
@@ -161,7 +164,7 @@ bool WrappedOpenGL::Serialise_glCompileShader(GLuint shader)
 		else
 		{
 			shadDetails.prog = sepProg;
-			MakeShaderReflection(m_Real, shadDetails.type, sepProg, shadDetails.reflection);
+			MakeShaderReflection(m_Real, shadDetails.type, sepProg, shadDetails.reflection, pointSizeUsed, clipDistanceUsed);
 			
 			create_array_uninit(shadDetails.reflection.DebugInfo.files, shadDetails.sources.size());
 			for(size_t i=0; i < shadDetails.sources.size(); i++)
@@ -341,10 +344,13 @@ bool WrappedOpenGL::Serialise_glCreateShaderProgramv(GLuint program, GLenum type
 
 		auto &shadDetails = m_Shaders[liveId];
 
+		bool pointSizeUsed = false, clipDistanceUsed = false;
+		if(Type == eGL_VERTEX_SHADER) CheckVertexOutputUses(src, pointSizeUsed, clipDistanceUsed);
+
 		shadDetails.type = Type;
 		shadDetails.sources.swap(src);
 		shadDetails.prog = real;
-		MakeShaderReflection(m_Real, Type, real, shadDetails.reflection);
+		MakeShaderReflection(m_Real, Type, real, shadDetails.reflection, pointSizeUsed, clipDistanceUsed);
 
 		create_array_uninit(shadDetails.reflection.DebugInfo.files, shadDetails.sources.size());
 		for(size_t i=0; i < shadDetails.sources.size(); i++)
@@ -1063,6 +1069,9 @@ bool WrappedOpenGL::Serialise_glCompileShaderIncludeARB(GLuint shader, GLsizei c
 		for(int32_t i=0; i < Count; i++)
 			shadDetails.includepaths.push_back(pathstrings[i]);
 
+		bool pointSizeUsed = false, clipDistanceUsed = false;
+		if(shadDetails.type == eGL_VERTEX_SHADER) CheckVertexOutputUses(shadDetails.sources, pointSizeUsed, clipDistanceUsed);
+
 		GLuint sepProg = MakeSeparableShaderProgram(m_Real, shadDetails.type, shadDetails.sources, &paths);
 
 		if(sepProg == 0)
@@ -1072,7 +1081,7 @@ bool WrappedOpenGL::Serialise_glCompileShaderIncludeARB(GLuint shader, GLsizei c
 		else
 		{
 			shadDetails.prog = sepProg;
-			MakeShaderReflection(m_Real, shadDetails.type, sepProg, shadDetails.reflection);
+			MakeShaderReflection(m_Real, shadDetails.type, sepProg, shadDetails.reflection, pointSizeUsed, clipDistanceUsed);
 			
 			create_array_uninit(shadDetails.reflection.DebugInfo.files, shadDetails.sources.size());
 			for(size_t i=0; i < shadDetails.sources.size(); i++)