diff --git a/mozilla/js/rhino/src/org/mozilla/javascript/BaseFunction.java b/mozilla/js/rhino/src/org/mozilla/javascript/BaseFunction.java
index 88b8e2f02b4..aaafefe1195 100644
--- a/mozilla/js/rhino/src/org/mozilla/javascript/BaseFunction.java
+++ b/mozilla/js/rhino/src/org/mozilla/javascript/BaseFunction.java
@@ -309,11 +309,11 @@ public class BaseFunction extends IdScriptableObject implements Function
             final Scriptable boundThis;
             final Object[] boundArgs;
             if (argc > 0) {
-              boundThis = ScriptRuntime.toObject(cx, scope, args[0]);
+              boundThis = ScriptRuntime.toObjectOrNull(cx, args[0], scope);
               boundArgs = new Object[argc-1];
               System.arraycopy(args, 1, boundArgs, 0, argc-1);
             } else {
-              boundThis = ScriptRuntime.toObject(cx, scope, Undefined.instance);
+              boundThis = null;
               boundArgs = ScriptRuntime.emptyArgs;
             }
             return new BoundFunction(cx, scope, targetFunction, boundThis, boundArgs);
diff --git a/mozilla/js/rhino/src/org/mozilla/javascript/BoundFunction.java b/mozilla/js/rhino/src/org/mozilla/javascript/BoundFunction.java
index 6f26b702cc0..9705cf5c650 100644
--- a/mozilla/js/rhino/src/org/mozilla/javascript/BoundFunction.java
+++ b/mozilla/js/rhino/src/org/mozilla/javascript/BoundFunction.java
@@ -79,7 +79,8 @@ public class BoundFunction extends BaseFunction {
   @Override
   public Object call(Context cx, Scriptable scope, Scriptable thisObj, Object[] extraArgs)
   {
-    return targetFunction.call(cx, scope, boundThis, concat(boundArgs, extraArgs));
+    Scriptable callThis = boundThis != null ? boundThis : ScriptRuntime.getTopCallScope(cx);
+    return targetFunction.call(cx, scope, callThis, concat(boundArgs, extraArgs));
   }
 
   @Override