diff --git a/dix/dix_priv.h b/dix/dix_priv.h
index c3dc45fac1..550091937a 100644
--- a/dix/dix_priv.h
+++ b/dix/dix_priv.h
@@ -38,6 +38,13 @@
         }                                       \
     } while (0)
 
+/* static assert for protocol structure sizes */
+#ifndef __size_assert
+#define __size_assert(what, howmuch) \
+  typedef char what##_size_wrong_[( !!(sizeof(what) == howmuch) )*2-1 ]
+#endif
+#define XTYPE_SIZE_ASSERT(typename) __size_assert(typename,SIZEOF(typename))
+
 /* server setting: maximum size for big requests */
 #define MAX_BIG_REQUEST_SIZE 4194303
 extern long maxBigRequestSize;