diff --git a/sys/net/rtsock.c b/sys/net/rtsock.c
--- a/sys/net/rtsock.c
+++ b/sys/net/rtsock.c
@@ -1503,6 +1503,7 @@
 			return (ENOBUFS);
 		fill_sockaddr_inet(mask_sa, mask);
 		info->rti_info[RTAX_NETMASK] = (struct sockaddr *)mask_sa;
+		info->rti_flags &= ~RTF_HOST;
 	} else
 		remove_netmask(info);
 
@@ -1563,6 +1564,7 @@
 			return (ENOBUFS);
 		fill_sockaddr_inet6((struct sockaddr_in6 *)sa, &mask, 0);
 		info->rti_info[RTAX_NETMASK] = sa;
+		info->rti_flags &= ~RTF_HOST;
 	} else
 		remove_netmask(info);