diff --git a/tool/playground/T.g b/tool/playground/T.g
index 819d11e52..1a3aba177 100644
--- a/tool/playground/T.g
+++ b/tool/playground/T.g
@@ -1,6 +1,6 @@
 grammar T;
 
-s : rule ;
+s : R ;
+
+R : 'x' EOF;
 
-rule : A # X
-  ;
diff --git a/tool/src/org/antlr/v4/tool/GrammarTransformPipeline.java b/tool/src/org/antlr/v4/tool/GrammarTransformPipeline.java
index dbceaa87e..83b4c56f1 100644
--- a/tool/src/org/antlr/v4/tool/GrammarTransformPipeline.java
+++ b/tool/src/org/antlr/v4/tool/GrammarTransformPipeline.java
@@ -279,7 +279,7 @@ public class GrammarTransformPipeline {
 		GrammarRootAST combinedAST = combinedGrammar.ast;
 		//tool.log("grammar", "before="+combinedAST.toStringTree());
 		GrammarASTAdaptor adaptor = new GrammarASTAdaptor(combinedAST.token.getInputStream());
-		GrammarAST[] elements = combinedAST.getChildren().toArray(new GrammarAST[0]);
+		GrammarAST[] elements = (GrammarAST[])combinedAST.getChildren().toArray(new GrammarAST[0]);
 
 		// MAKE A GRAMMAR ROOT and ID
 		String lexerName = combinedAST.getChild(0).getText()+"Lexer";
@@ -295,7 +295,7 @@ public class GrammarTransformPipeline {
 		if ( optionsRoot!=null ) {
 			GrammarAST lexerOptionsRoot = (GrammarAST)adaptor.dupNode(optionsRoot);
 			lexerAST.addChild(lexerOptionsRoot);
-			GrammarAST[] options = optionsRoot.getChildren().toArray(new GrammarAST[0]);
+			GrammarAST[] options = (GrammarAST[])optionsRoot.getChildren().toArray(new GrammarAST[0]);
 			for (GrammarAST o : options) {
 				String optionName = o.getChild(0).getText();
 				if ( Grammar.lexerOptions.contains(optionName) &&