diff --git a/sys/netinet/in.h b/sys/netinet/in.h
index 403c534e8333..5b83669cb9a8 100644
--- a/sys/netinet/in.h
+++ b/sys/netinet/in.h
@@ -483,6 +483,7 @@ int	 in_broadcast __P((struct in_addr, struct ifnet *));
 int	 in_canforward __P((struct in_addr));
 int	 in_localaddr __P((struct in_addr));
 char 	*inet_ntoa __P((struct in_addr)); /* in libkern */
+char	*inet_ntoa_r __P((struct in_addr ina, char *buf)); /* in libkern */
 
 int	prison_ip __P((struct proc *p, int flag, u_int32_t *ip));
 void	prison_remote_ip __P((struct proc *p, int flag, u_int32_t *ip));