diff --git a/reactos/dll/win32/opengl32/gl.c b/reactos/dll/win32/opengl32/gl.c
index 249ed529819..787750e4000 100644
--- a/reactos/dll/win32/opengl32/gl.c
+++ b/reactos/dll/win32/opengl32/gl.c
@@ -25,6 +25,9 @@
 #include <windows.h>
 #include "teb.h"
 
+#define C_ASSERT(e) extern char __C_ASSERT__[(e)?1:-1]
+C_ASSERT(FIELD_OFFSET(TEB, glTable) == 0xbe8);
+
 #include "opengl32.h"
 
 int STDCALL glEmptyFunc0() { return 0; }