diff --git a/pyopencl/cffi_cl.py b/pyopencl/cffi_cl.py
index d2551461b2cd2389429a2b8d235d9845e34c25c4..763aff8c46c45eb2efa8cef5b6716dc206cd7b22 100644
--- a/pyopencl/cffi_cl.py
+++ b/pyopencl/cffi_cl.py
@@ -515,8 +515,8 @@ def _parse_context_properties(properties):
                 'CGL_SHAREGROUP_KHR',
                 )]:
 
-            val = (ctypes.cast(value, ctypes.c_void_p)).value
-            if val is None:
+            val = int(_ffi.cast('intptr_t', value))
+            if not val:
                 raise LogicError("Context", status_code.INVALID_VALUE,
                                  "You most likely have not initialized "
                                  "OpenGL properly.")