diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index e689b47..cc2eefd 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -458,7 +458,9 @@ struct sk_buff {
 	union {
 		__u32		mark;
 		__u32		dropcount;
+#ifndef __GENKSYMS__
 		__u32		avail_size;
+#endif
 	};
 
 	__u16			vlan_tci;