diff --git a/sys/src/9/ip/chandial.c b/sys/src/9/ip/chandial.c
index 38139ceec..58fc007bc 100644
--- a/sys/src/9/ip/chandial.c
+++ b/sys/src/9/ip/chandial.c
@@ -40,7 +40,7 @@ chandial(char *dest, char *local, char *dir, Chan **ctlp)
 	ds.ctlp = ctlp;
 
 	_dial_string_parse(dest, &ds);
-	if(ds.netdir == 0)
+	if(ds.netdir == nil)
 		ds.netdir = "/net";
 
 	/* no connection server, don't translate */
@@ -109,11 +109,13 @@ _dial_string_parse(char *str, DS *ds)
 		ds->rem = ds->buf;
 	} else {
 		if(*ds->buf != '/' && *ds->buf != '#'){
-			ds->netdir = 0;
+			ds->netdir = nil;
 			ds->proto = ds->buf;
 		} else {
-			for(p2 = p; *p2 != '/'; p2--)
+			for(p2 = p; *p2 != '/' && p2 != ds->buf; p2--)
 				;
+			if(p2 == ds->buf)
+				error(Ebadarg);
 			*p2++ = 0;
 			ds->netdir = ds->buf;
 			ds->proto = p2;