diff --git a/Shorewall/Perl/Shorewall/Rules.pm b/Shorewall/Perl/Shorewall/Rules.pm
index ed08c8546..8f7f3d211 100644
--- a/Shorewall/Perl/Shorewall/Rules.pm
+++ b/Shorewall/Perl/Shorewall/Rules.pm
@@ -1129,6 +1129,8 @@ sub merge_levels ($$) {
 
     my $target   = $subparts[0];
 
+    fatal_error "Missing ACTION" unless supplied $target;
+
     push @subparts, '' while @subparts < 3;   #Avoid undefined values
 
     my $sublevel = $subparts[1];