diff --git a/kiss b/kiss
index 73541c2..166a5d2 100755
--- a/kiss
+++ b/kiss
@@ -131,7 +131,7 @@ as_user() {
     printf 'Using '%s' (to become %s)\n' "$cmd_su" "$user"
 
     case ${cmd_su##*/} in
-        su) "$cmd_su" -c "$* <&3" "$user" 3<&0 </dev/tty ;;
+        su) "$cmd_su" -c "$* <&3" - "$user" 3<&0 </dev/tty ;;
          *) "$cmd_su" -u "$user" -- "$@"
     esac
 }