diff --git a/freebsd/net/if_gre.h b/freebsd/net/if_gre.h
index 852d879ff..6eba312c8 100644
--- a/freebsd/net/if_gre.h
+++ b/freebsd/net/if_gre.h
@@ -52,13 +52,22 @@ struct grehdr {
 struct greip {
 	struct ip	gi_ip;
 	struct grehdr	gi_gre;
+#ifndef FSTACK
+} __packed;
+#else
 } __packed __aligned(2);
+#endif
 
 struct greudp {
 	struct ip	gi_ip;
 	struct udphdr	gi_udp;
 	struct grehdr	gi_gre;
+#ifndef FSTACK
+} __packed;
+#else
 } __packed __aligned(2);
+#endif
+
 #endif /* INET */
 
 #ifdef INET6