diff --git a/js/rhino/src/org/mozilla/javascript/IRFactory.java b/js/rhino/src/org/mozilla/javascript/IRFactory.java
index 27fc391f0171..908094adf70a 100644
--- a/js/rhino/src/org/mozilla/javascript/IRFactory.java
+++ b/js/rhino/src/org/mozilla/javascript/IRFactory.java
@@ -1072,7 +1072,6 @@ final class IRFactory
         switch (node.getType()) {
           case Token.FALSE:
           case Token.NULL:
-          case Token.UNDEFINED:
             return ALWAYS_FALSE_BOOLEAN;
           case Token.TRUE:
             return ALWAYS_TRUE_BOOLEAN;
diff --git a/js/rhino/src/org/mozilla/javascript/Interpreter.java b/js/rhino/src/org/mozilla/javascript/Interpreter.java
index 5871b73bae9c..1ed39bd7ff93 100644
--- a/js/rhino/src/org/mozilla/javascript/Interpreter.java
+++ b/js/rhino/src/org/mozilla/javascript/Interpreter.java
@@ -129,8 +129,10 @@ public class Interpreter
         Icode_GETVAR1                   = -43,
         Icode_SETVAR1                   = -44,
 
+        Icode_UNDEF                     = -45,
+
     // Last icode
-        MIN_ICODE                       = -44;
+        MIN_ICODE                       = -45;
 
     static {
         // Checks for byte code consistencies, good compiler can eliminate them
@@ -727,7 +729,7 @@ public class Interpreter
                 iCodeTop = generateICode(child, iCodeTop);
                 if (type == Token.VOID) {
                     iCodeTop = addToken(Token.POP, iCodeTop);
-                    iCodeTop = addToken(Token.UNDEFINED, iCodeTop);
+                    iCodeTop = addIcode(Icode_UNDEF, iCodeTop);
                 } else {
                     iCodeTop = addToken(type, iCodeTop);
                 }
@@ -1008,7 +1010,6 @@ public class Interpreter
             case Token.THISFN:
             case Token.FALSE:
             case Token.TRUE:
-            case Token.UNDEFINED:
                 stackDelta = 1;
                 iCodeTop = addToken(type, iCodeTop);
                 itsStackDepth++;
@@ -1640,6 +1641,7 @@ public class Interpreter
           case Icode_REG_STR4:         return "LOAD_STR4";
           case Icode_GETVAR1:          return "GETVAR1";
           case Icode_SETVAR1:          return "SETVAR1";
+          case Icode_UNDEF:            return "UNDEF";
         }
 
         // icode without name
@@ -2776,8 +2778,8 @@ switch (op) {
     case Token.TRUE :
         stack[++stackTop] = Boolean.TRUE;
         continue Loop;
-    case Token.UNDEFINED :
-        stack[++stackTop] = Undefined.instance;
+    case Icode_UNDEF :
+        stack[++stackTop] = undefined;
         continue Loop;
     case Token.ENTERWITH : {
         Object lhs = stack[stackTop];
diff --git a/js/rhino/src/org/mozilla/javascript/Token.java b/js/rhino/src/org/mozilla/javascript/Token.java
index b4054bdc6fe8..9d7f23a85c4e 100644
--- a/js/rhino/src/org/mozilla/javascript/Token.java
+++ b/js/rhino/src/org/mozilla/javascript/Token.java
@@ -131,7 +131,7 @@ public class Token
         LOCAL_LOAD  = 57,
         GETVAR      = 58,
         SETVAR      = 59,
-        UNDEFINED   = 60,
+// XXX removed unused UNDEFINED
         CATCH_SCOPE = 61,
         ENUM_INIT   = 62,
         ENUM_NEXT   = 63,
@@ -282,7 +282,6 @@ public class Token
           case LOCAL_LOAD:      return "LOCAL_LOAD";
           case GETVAR:          return "GETVAR";
           case SETVAR:          return "SETVAR";
-          case UNDEFINED:       return "UNDEFINED";
           case CATCH_SCOPE:     return "CATCH_SCOPE";
           case ENUM_INIT:       return "ENUM_INIT";
           case ENUM_NEXT:       return "ENUM_NEXT";
diff --git a/js/rhino/src/org/mozilla/javascript/optimizer/Codegen.java b/js/rhino/src/org/mozilla/javascript/optimizer/Codegen.java
index 13cefe10a2b8..95e3dc131c7c 100644
--- a/js/rhino/src/org/mozilla/javascript/optimizer/Codegen.java
+++ b/js/rhino/src/org/mozilla/javascript/optimizer/Codegen.java
@@ -1449,10 +1449,6 @@ class BodyCodegen
                         "FALSE", "Ljava/lang/Boolean;");
                 break;
 
-              case Token.UNDEFINED:
-                Codegen.pushUndefined(cfw);
-                break;
-
               case Token.REGEXP:
                 visitRegexp(node);
                 break;