diff --git a/bin/9l b/bin/9l
index d7c9e2dd..3b8cf680 100755
--- a/bin/9l
+++ b/bin/9l
@@ -1,5 +1,7 @@
 #!/bin/sh
 
+[ "$1" = "" ] && exit 1
+
 test -f $PLAN9/config && . $PLAN9/config
 libsl=""
 frameworks=""