--- old/src/jdk.scripting.nashorn/share/classes/jdk/nashorn/internal/codegen/Lower.java	2014-12-08 15:58:14.961725873 +0100
+++ new/src/jdk.scripting.nashorn/share/classes/jdk/nashorn/internal/codegen/Lower.java	2014-12-08 15:58:14.841725875 +0100
@@ -34,6 +34,8 @@
 import java.util.Collections;
 import java.util.List;
 import java.util.ListIterator;
+import java.util.regex.Pattern;
+import jdk.nashorn.internal.ir.AccessNode;
 import jdk.nashorn.internal.ir.BaseNode;
 import jdk.nashorn.internal.ir.BinaryNode;
 import jdk.nashorn.internal.ir.Block;
@@ -52,6 +54,7 @@
 import jdk.nashorn.internal.ir.FunctionNode.CompilationState;
 import jdk.nashorn.internal.ir.IdentNode;
 import jdk.nashorn.internal.ir.IfNode;
+import jdk.nashorn.internal.ir.IndexNode;
 import jdk.nashorn.internal.ir.JumpStatement;
 import jdk.nashorn.internal.ir.LabelNode;
 import jdk.nashorn.internal.ir.LexicalContext;
@@ -93,6 +96,10 @@
 
     private final DebugLogger log;
 
+    // Conservative pattern to test if element names consist of characters valid for identifiers.
+    // This matches any non-zero length alphanumeric string including _ and $ and not starting with a digit.
+    private static Pattern SAFE_PROPERTY_NAME = Pattern.compile("[a-zA-Z_$][\\w$]*");
+
     /**
      * Constructor.
      */
@@ -140,7 +147,7 @@
             }
         });
 
-        this.log       = initLogger(compiler.getContext());
+        this.log = initLogger(compiler.getContext());
     }
 
     @Override
@@ -181,6 +188,31 @@
     }
 
     @Override
+    public Node leaveIndexNode(final IndexNode indexNode) {
+        final String name = getConstantPropertyName(indexNode.getIndex());
+        if (name != null) {
+            // If index node is a constant property name convert index node to access node.
+            assert Token.descType(indexNode.getToken()) == TokenType.LBRACKET;
+            return new AccessNode(indexNode.getToken(), indexNode.getFinish(), indexNode.getBase(), name);
+        }
+        return super.leaveIndexNode(indexNode);
+    }
+
+    // If expression is a primitive literal that is not an array index and does return its string value. Else return null.
+    private static String getConstantPropertyName(final Expression expression) {
+        if (expression instanceof LiteralNode.PrimitiveLiteralNode) {
+            final LiteralNode<?> literal = (LiteralNode) expression;
+            if (!literal.isNumeric()) {
+                final String str = literal.getString();
+                if (SAFE_PROPERTY_NAME.matcher(str).matches()) {
+                    return str;
+                }
+            }
+        }
+        return null;
+    }
+
+    @Override
     public Node leaveExpressionStatement(final ExpressionStatement expressionStatement) {
         final Expression expr = expressionStatement.getExpression();
         ExpressionStatement node = expressionStatement;