diff --git a/Shorewall/Perl/Shorewall/Chains.pm b/Shorewall/Perl/Shorewall/Chains.pm
index a1332351e..4274d992b 100644
--- a/Shorewall/Perl/Shorewall/Chains.pm
+++ b/Shorewall/Perl/Shorewall/Chains.pm
@@ -1084,6 +1084,8 @@ sub delete_jumps ( $$ ) {
 	}
     }
 
+    assert( ! $refs );
+
     delete $toref->{references}{$from};
 
     unless ( @{$toref->{rules}} ) {