--- a/lib/perl5/SmilesScripts/Isomorphism.pm
+++ b/lib/perl5/SmilesScripts/Isomorphism.pm
@@ -374,7 +374,7 @@
 
     for my $moiety (@$moieties) {
         for my $vertex ($moiety->vertices) {
-            $vertex->{symbol} = 'X';
+            $vertex->{symbol} = '*';
         }
     }