diff --git a/tool/src/org/antlr/v4/codegen/OutputModelWalker.java b/tool/src/org/antlr/v4/codegen/OutputModelWalker.java
index 5b62f0b4e..544489656 100644
--- a/tool/src/org/antlr/v4/codegen/OutputModelWalker.java
+++ b/tool/src/org/antlr/v4/codegen/OutputModelWalker.java
@@ -30,6 +30,7 @@
 package org.antlr.v4.codegen;
 
 import org.antlr.v4.Tool;
+import org.antlr.v4.codegen.model.ModelElement;
 import org.antlr.v4.codegen.model.OutputModelObject;
 import org.antlr.v4.tool.ErrorType;
 import org.stringtemplate.v4.*;
@@ -94,13 +95,24 @@ public class OutputModelWalker {
 		st.add(modelArgName, omo);
 
 		// COMPUTE STs FOR EACH NESTED MODEL OBJECT MARKED WITH @ModelElement AND MAKE ST ATTRIBUTE
+		Set<String> usedFieldNames = new HashSet<String>();
 		Field fields[] = cl.getFields();
 		for (Field fi : fields) {
-			Annotation[] annotations = fi.getAnnotations();
-			if ( annotations.length==0 ) continue;
+			ModelElement annotation = fi.getAnnotation(ModelElement.class);
+			if (annotation == null) {
+				continue;
+			}
+
 			String fieldName = fi.getName();
+
+			if (!usedFieldNames.add(fieldName)) {
+				tool.errMgr.toolError(ErrorType.INTERNAL_ERROR, "Model object " + omo.getClass().getSimpleName() + " has multiple fields named '" + fieldName + "'");
+				continue;
+			}
+
 			// Just don't set @ModelElement fields w/o formal arg in target ST
 			if ( formalArgs.get(fieldName)==null ) continue;
+
 			try {
 				Object o = fi.get(omo);
 				if ( o instanceof OutputModelObject ) {  // SINGLE MODEL OBJECT?
diff --git a/tool/src/org/antlr/v4/codegen/model/LL1PlusBlock.java b/tool/src/org/antlr/v4/codegen/model/LL1PlusBlock.java
index eebb3ba7c..e495249e5 100644
--- a/tool/src/org/antlr/v4/codegen/model/LL1PlusBlock.java
+++ b/tool/src/org/antlr/v4/codegen/model/LL1PlusBlock.java
@@ -46,7 +46,6 @@ public class LL1PlusBlock extends LL1Loop {
 	public String loopCounterVar;
 	public String[] exitLook;
 
-	@ModelElement public SrcOp loopExpr;
 	@ModelElement public ThrowNoViableAlt error;
 
 	public LL1PlusBlock(OutputModelFactory factory, GrammarAST plusRoot, List<CodeBlockForAlt> alts) {