diff --git a/renderdoc/driver/gl/gl_shader_refl.cpp b/renderdoc/driver/gl/gl_shader_refl.cpp
index a9a83d05b..c3cea1b4f 100644
--- a/renderdoc/driver/gl/gl_shader_refl.cpp
+++ b/renderdoc/driver/gl/gl_shader_refl.cpp
@@ -96,14 +96,14 @@ void copy(rdctype::array<ShaderConstant> &outvars, const vector<DynShaderConstan
 	}
 }
 
-void CheckVertexOutputUses(vector<string> sources, bool &pointSizeUsed, bool &clipDistanceUsed)
+void CheckVertexOutputUses(const vector<string> &sources, bool &pointSizeUsed, bool &clipDistanceUsed)
 {
 	pointSizeUsed = false;
 	clipDistanceUsed = false;
 
 	for(size_t i=0; i < sources.size(); i++)
 	{
-		string &s = sources[i];
+		const string &s = sources[i];
 
 		size_t offs = 0;
 
diff --git a/renderdoc/driver/gl/gl_shader_refl.h b/renderdoc/driver/gl/gl_shader_refl.h
index 2c8adcff7..61d354a72 100644
--- a/renderdoc/driver/gl/gl_shader_refl.h
+++ b/renderdoc/driver/gl/gl_shader_refl.h
@@ -28,4 +28,4 @@
 
 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);
+void CheckVertexOutputUses(const std::vector<std::string> &sources, bool &pointSizeUsed, bool &clipDistanceUsed);