diff --git a/sys/net/radix_mpath.c b/sys/net/radix_mpath.c
index 871d436cf750..98d7d6c430b0 100644
--- a/sys/net/radix_mpath.c
+++ b/sys/net/radix_mpath.c
@@ -36,6 +36,8 @@
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include "opt_inet6.h"
+
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/malloc.h>