diff --git a/reactos/include/reactos/win32k/ntuser.h b/reactos/include/reactos/win32k/ntuser.h
index 007fa887200..b8019ac4527 100644
--- a/reactos/include/reactos/win32k/ntuser.h
+++ b/reactos/include/reactos/win32k/ntuser.h
@@ -216,8 +216,8 @@ typedef struct _CLIENTINFO
     PPROCESSINFO ppi;
 } CLIENTINFO, *PCLIENTINFO;
 
-/* Make sure it fits exactly into the TEB */
-C_ASSERT(sizeof(CLIENTINFO) == FIELD_OFFSET(TEB, glDispatchTable) - FIELD_OFFSET(TEB, Win32ClientInfo));
+/* Make sure it fits into the TEB */
+C_ASSERT(sizeof(CLIENTINFO) <= sizeof(((PTEB)0)->Win32ClientInfo));
 
 #define GetWin32ClientInfo() ((PCLIENTINFO)(NtCurrentTeb()->Win32ClientInfo))