--- a/glcontext/wgl.cpp
+++ b/glcontext/wgl.cpp
@@ -290,7 +290,7 @@
 
 PyType_Slot GLContext_slots[] = {
     {Py_tp_methods, GLContext_methods},
-    {Py_tp_dealloc, GLContext_dealloc},
+    {Py_tp_dealloc, (void*)GLContext_dealloc},
     {},
 };