diff --git a/include/dix.h b/include/dix.h
index 991a3ce88..e0c6ed84f 100644
--- a/include/dix.h
+++ b/include/dix.h
@@ -76,7 +76,8 @@ SOFTWARE.
 
 #define REQUEST_FIXED_SIZE(req, n)\
     if (((sizeof(req) >> 2) > client->req_len) || \
-        (((sizeof(req) + (n) + 3) >> 2) != client->req_len)) \
+        ((n >> 2) >= client->req_len) || \
+        ((((uint64_t) sizeof(req) + (n) + 3) >> 2) != (uint64_t) client->req_len))  \
          return(BadLength)
 
 #define LEGAL_NEW_RESOURCE(id,client)\