1.1 --- a/rt/vm/src/main/java/org/apidesign/vm4brwsr/VM.java	Fri Feb 27 13:50:37 2015 +0100
     1.2 +++ b/rt/vm/src/main/java/org/apidesign/vm4brwsr/VM.java	Fri Feb 27 18:11:54 2015 +0100
     1.3 @@ -291,11 +291,7 @@
     1.4      
     1.5      @Override
     1.6      protected boolean requireReference(String cn) {
     1.7 -        if (references.contains(cn)) {
     1.8 -            return false;
     1.9 -        }
    1.10 -        references.add(cn);
    1.11 -        return true;
    1.12 +        return references.addIfMissing(cn);
    1.13      }
    1.14  
    1.15      @Override