diff --git a/demo/gpudemo/premake4.lua b/demo/gpudemo/premake4.lua
index 38b9ee4ed..0914522ae 100644
--- a/demo/gpudemo/premake4.lua
+++ b/demo/gpudemo/premake4.lua
@@ -65,6 +65,9 @@ function createProject(vendor)
 			"../../opencl/parallel_primitives/host/btPrefixScanCL.h",
 			"../../opencl/parallel_primitives/host/btRadixSort32CL.cpp",
 			"../../opencl/parallel_primitives/host/btRadixSort32CL.h",
+			"../../opencl/gpu_rigidbody/host/**.cpp",
+			"../../opencl/gpu_rigidbody/host/**.h",
+
 		}
 
 		if os.is("Windows") then 
diff --git a/opencl/gpu_rigidbody/host/btTypedConstraint.h b/opencl/gpu_rigidbody/host/btTypedConstraint.h
index 41156a19c..6c0ab2003 100644
--- a/opencl/gpu_rigidbody/host/btTypedConstraint.h
+++ b/opencl/gpu_rigidbody/host/btTypedConstraint.h
@@ -322,10 +322,10 @@ public:
 	///return the local value of parameter
 	virtual	btScalar getParam(int num, int axis = -1) const = 0;
 	
-	virtual	int	calculateSerializeBufferSize() const;
+	virtual	int	calculateSerializeBufferSize() const=0;
 
 	///fills the dataBuffer and returns the struct name (and 0 on failure)
-	virtual	const char*	serialize(void* dataBuffer, btSerializer* serializer) const;
+	virtual	const char*	serialize(void* dataBuffer, btSerializer* serializer) const=0;
 
 };