Index: sbin/ifconfig/af_inet.c
===================================================================
--- sbin/ifconfig/af_inet.c
+++ sbin/ifconfig/af_inet.c
@@ -464,8 +464,7 @@
 warn_nomask(int ifflags)
 {
     if ((ifflags & (IFF_POINTOPOINT | IFF_LOOPBACK)) == 0) {
-	warnx("WARNING: setting interface address without mask "
-	    "is deprecated,\ndefault mask may not be correct.");
+	errx(1, "ERROR: setting interface address without mask is no longer supported.");
     }
 }