CUDA copy OpenGL mapped buffer

Hi, I have an OpenGL buffer that I have mapped to CUDA using the deprecated API, and I would like to copy the data that is inside it, this is what I’ve tried so far, but I’m getting an invalid argument error:

// ... create OpenGL buffer ...
// Register OpenGL buffer

// Map to cuda memory
int* buffer;
COMPUTE_SAFE(cudaGLMapBufferObject(reinterpret_cast<void**>(&buffer), vertexBufferID));

// Create a copy of the buffer
int* bufferCopy;
COMPUTE_SAFE(cudaMalloc((void**)&bufferCopy, elementCount * sizeof(int)));
// Note that the following line produces the error
COMPUTE_SAFE(cudaMemcpy(bufferCopy, buffer, elementCount * sizeof(int), cudaMemcpyDeviceToDevice));

// ... Free the memory and unmap the vertex buffer ...

Note that I’ve written this inside of a browser and have not tested this, however it should still produce the same error. Also note that the OpenGL interop works just fine without the bufferCopy thing.

Any help is greatly appreciated.