Index: sys/net/route.h
===================================================================
RCS file: /cvsroot/src/sys/net/route.h,v
retrieving revision 1.110
diff -p -u -r1.110 route.h
--- sys/net/route.h	16 Dec 2016 20:11:52 -0000	1.110
+++ sys/net/route.h	18 Dec 2016 18:48:43 -0000
@@ -286,7 +286,8 @@ struct rt_msghdr {
 #define RTAX_TAG	8	/* route tag */
 #define RTAX_MAX	9	/* size of array to allocate */
 
-#define RT_ROUNDUP2(a, n)	((a) > 0 ? (1 + (((a) - 1) | ((n) - 1))) : (n))
+#define RT_ROUNDUP2(a, n)	\
+	((a) > 0 ? (1 + (((a) - 1) | ((n) - 1))) : (n) + 0*(a))
 #define RT_ROUNDUP(a)		RT_ROUNDUP2((a), sizeof(uint64_t))
 #define RT_ADVANCE(x, n)	(x += RT_ROUNDUP((n)->sa_len))