Hi! I've found a bug in gl binding. The unmarshal function is wrong, because in this case there is no gl_TEXTURE0 offset. maxTextureUnit :: GettableStateVar TextureUnit maxTextureUnit = makeGettableStateVar (getEnum1 unmarshalTextureUnit GetMaxTextureUnits) unmarshalTextureUnit :: GLenum -> TextureUnit unmarshalTextureUnit x = TextureUnit (fromIntegral (x - gl_TEXTURE0)) Cheers, Csaba Hruska