--- openflow-2013-03-25.h	2015-07-23 09:54:17.204479364 -0700
+++ openflow-2012-12-11.h	2015-07-23 09:54:17.208479364 -0700
@@ -406,7 +406,8 @@
      * In summary, ofp_match is padded as needed, to make its overall size
      * a multiple of 8, to preserve alignement in structures using it.
      */
-    uint8_t oxm_fields[4];     /* OXMs start here - Make compiler happy */
+    uint8_t oxm_fields[0];     /* 0 or more OXM match fields */
+    uint8_t pad[4];            /* Zero bytes - see above for sizing */
 };
 OFP_ASSERT(sizeof(struct ofp_match) == 8);