--- tool/src/main/java/org/antlr/tool/CompositeGrammar.java.orig 2014-05-30 00:12:33.360503545 +0100 +++ tool/src/main/java/org/antlr/tool/CompositeGrammar.java 2014-05-30 00:13:38.533423946 +0100 @@ -219,7 +219,7 @@ public List<Grammar> getIndirectDelegates(Grammar g) { List<Grammar> direct = getDirectDelegates(g); List<Grammar> delegates = getDelegates(g); - delegates.removeAll(direct); + if ( direct!=null ) delegates.removeAll(direct); return delegates; }