diff --git a/js/rhino/src/org/mozilla/javascript/Interpreter.java b/js/rhino/src/org/mozilla/javascript/Interpreter.java
index 530974c5c05..824cea5bb9e 100644
--- a/js/rhino/src/org/mozilla/javascript/Interpreter.java
+++ b/js/rhino/src/org/mozilla/javascript/Interpreter.java
@@ -1924,7 +1924,7 @@ public class Interpreter
         --stackTop;
         Object lhs = stack[stackTop];
         if (lhs == DBL_MRK) lhs = doubleWrap(sDbl[stackTop]);
-        boolean valBln = ScriptRuntime.instanceOf(scope, lhs, rhs);
+        boolean valBln = ScriptRuntime.instanceOf(lhs, rhs, scope);
         stack[stackTop] = valBln ? Boolean.TRUE : Boolean.FALSE;
         break;
     }
diff --git a/js/rhino/src/org/mozilla/javascript/NativeArray.java b/js/rhino/src/org/mozilla/javascript/NativeArray.java
index ecec663f8b1..a2b75444f55 100644
--- a/js/rhino/src/org/mozilla/javascript/NativeArray.java
+++ b/js/rhino/src/org/mozilla/javascript/NativeArray.java
@@ -1023,7 +1023,7 @@ public class NativeArray extends IdScriptable {
         /* Put the target in the result array; only add it as an array
          * if it looks like one.
          */
-        if (ScriptRuntime.instanceOf(scope, thisObj, ctor)) {
+        if (ScriptRuntime.instanceOf(thisObj, ctor, scope)) {
             length = getLengthProperty(thisObj);
 
             // Copy from the target object into the result
@@ -1040,7 +1040,7 @@ public class NativeArray extends IdScriptable {
          * elements separately; otherwise, just copy the argument.
          */
         for (int i = 0; i < args.length; i++) {
-            if (ScriptRuntime.instanceOf(scope, args[i], ctor)) {
+            if (ScriptRuntime.instanceOf(args[i], ctor, scope)) {
                 // ScriptRuntime.instanceOf => instanceof Scriptable
                 Scriptable arg = (Scriptable)args[i];
                 length = getLengthProperty(arg);
diff --git a/js/rhino/src/org/mozilla/javascript/ScriptRuntime.java b/js/rhino/src/org/mozilla/javascript/ScriptRuntime.java
index f1f796f16ab..c190102995b 100644
--- a/js/rhino/src/org/mozilla/javascript/ScriptRuntime.java
+++ b/js/rhino/src/org/mozilla/javascript/ScriptRuntime.java
@@ -1638,7 +1638,8 @@ public class ScriptRuntime {
      *
      * @return a instanceof b
      */
-    public static boolean instanceOf(Scriptable scope, Object a, Object b) {
+    public static boolean instanceOf(Object a, Object b, Scriptable scope) 
+    {
         // Check RHS is an object
         if (! (b instanceof Scriptable)) {
             throw NativeGlobal.typeError0("msg.instanceof.not.object", scope);
diff --git a/js/rhino/src/org/mozilla/javascript/optimizer/Codegen.java b/js/rhino/src/org/mozilla/javascript/optimizer/Codegen.java
index 979732170ee..3904e21b674 100644
--- a/js/rhino/src/org/mozilla/javascript/optimizer/Codegen.java
+++ b/js/rhino/src/org/mozilla/javascript/optimizer/Codegen.java
@@ -2552,24 +2552,12 @@ public class Codegen extends Interpreter {
             generateCodeFromNode(child.getNext(), node);
             genSimpleCompare(op, trueGOTO, falseGOTO);
         } else {
-            if (op == Token.INSTANCEOF) {
-                aload(variableObjectLocal);
-                generateCodeFromNode(child, node);
-                generateCodeFromNode(child.getNext(), node);
-                addScriptRuntimeInvoke(
-                    "instanceOf",
-                    "(Lorg/mozilla/javascript/Scriptable;"
-                    +"Ljava/lang/Object;"
-                    +"Ljava/lang/Object;"
-                    +")Z");
-                addByteCode(ByteCode.IFNE, trueGOTO);
-                addByteCode(ByteCode.GOTO, falseGOTO);
-            } else if (op == Token.IN) {
+            if (op == Token.INSTANCEOF || op == Token.IN) {
                 generateCodeFromNode(child, node);
                 generateCodeFromNode(child.getNext(), node);
                 aload(variableObjectLocal);
                 addScriptRuntimeInvoke(
-                    "in",
+                    (op == Token.INSTANCEOF) ? "instanceOf" : "in",
                     "(Ljava/lang/Object;"
                     +"Ljava/lang/Object;"
                     +"Lorg/mozilla/javascript/Scriptable;"
@@ -2699,24 +2687,14 @@ public class Codegen extends Interpreter {
                 || op == Token.INSTANCEOF
                 || op == Token.IN)
         {
-            if (op == Token.INSTANCEOF)
-                aload(variableObjectLocal);
             generateCodeFromNode(child, node);
             generateCodeFromNode(child.getNext(), node);
             int trueGOTO = acquireLabel();
             int skip = acquireLabel();
-            if (op == Token.INSTANCEOF) {
-                addScriptRuntimeInvoke(
-                    "instanceOf",
-                    "(Lorg/mozilla/javascript/Scriptable;"
-                    +"Ljava/lang/Object;"
-                    +"Ljava/lang/Object;"
-                    +")Z");
-                addByteCode(ByteCode.IFNE, trueGOTO);
-            } else if (op == Token.IN) {
+            if (op == Token.INSTANCEOF || op == Token.IN) {
                 aload(variableObjectLocal);
                 addScriptRuntimeInvoke(
-                    "in",
+                    (op == Token.INSTANCEOF) ? "instanceOf" : "in",
                     "(Ljava/lang/Object;"
                     +"Ljava/lang/Object;"
                     +"Lorg/mozilla/javascript/Scriptable;"