--- openflow-2014-09-08.h	2015-07-23 09:54:17.772479387 -0700
+++ openflow-2014-09-09.h	2015-07-23 09:54:17.780479388 -0700
@@ -1433,11 +1433,11 @@
     uint16_t n_bits;                /* Number of bits to copy. */
     uint16_t src_offset;            /* Starting bit offset in source. */
     uint16_t dst_offset;            /* Starting bit offset in destination. */
-    uint16_t oxm_id_len;            /* Length of oxm_ids. */
+    uint8_t pad[2];                 /* Align to 32 bits. */
     /* Followed by:
-     *   - Exactly (oxm_id_len) bytes containing the oxm_ids, then
-     *   - Exactly (12 + oxm_id_len + 7)/8*8 - (12 + oxm_id_len) (between 0
-     *     and 7) bytes of all-zero bytes */
+     *   - Exactly 64, 96 or 128 bytes containing the oxm_ids, then
+     *   - Enough 0-bytes (between 0 and 7) to make the action a whole
+     *     multiple of 8 bytes in length */
     uint32_t         oxm_ids[0];   /* Source and destination OXM headers */
 };
 OFP_ASSERT(sizeof(struct ofp_action_copy_field) == 12);