diff --git a/Shorewall-common/shorewall b/Shorewall-common/shorewall
index eb31f6e98..2df698345 100755
--- a/Shorewall-common/shorewall
+++ b/Shorewall-common/shorewall
@@ -515,6 +515,7 @@ compile_command() {
     case $# in
 	1)
 	    file=$1
+	    [ -d $file ] && echo "   ERROR: $file is a directory" >&2 && exit 2;
 	    ;;
 	2)
 	    [ -n "$SHOREWALL_DIR" ] && usage 2