diff --git a/js/src/jsinterp.cpp b/js/src/jsinterp.cpp
index aed46c813763..f712ef91896d 100644
--- a/js/src/jsinterp.cpp
+++ b/js/src/jsinterp.cpp
@@ -831,7 +831,8 @@ js_ComputeGlobalThis(JSContext *cx, JSBool lazy, jsval *argv)
             thisp = parent;
     }
 
-    OBJ_TO_OUTER_OBJECT(cx, thisp);
+    /* Some objects (e.g., With) delegate 'this' to another object. */
+    thisp = OBJ_THIS_OBJECT(cx, thisp);
     if (!thisp)
         return NULL;
     argv[-1] = OBJECT_TO_JSVAL(thisp);
@@ -855,18 +856,11 @@ ComputeThis(JSContext *cx, JSBool lazy, jsval *argv)
             return js_ComputeGlobalThis(cx, lazy, argv);
         }
 
-        OBJ_TO_OUTER_OBJECT(cx, thisp);
+        /* Some objects (e.g., With) delegate 'this' to another object. */
+        thisp = OBJ_THIS_OBJECT(cx, thisp);
         if (!thisp)
             return NULL;
         argv[-1] = OBJECT_TO_JSVAL(thisp);
-
-        if (thisp->map->ops->thisObject) {
-            /* Some objects (e.g., With) delegate 'this' to another object. */
-            thisp = thisp->map->ops->thisObject(cx, thisp);
-            if (!thisp)
-                return NULL;
-            argv[-1] = OBJECT_TO_JSVAL(thisp);
-       }
     }
     return thisp;
 }
@@ -1551,7 +1545,7 @@ js_Execute(JSContext *cx, JSObject *chain, JSScript *script,
 
     cx->fp = &frame;
     if (!down) {
-        OBJ_TO_OUTER_OBJECT(cx, frame.thisp);
+        frame.thisp = OBJ_THIS_OBJECT(cx, frame.thisp);
         if (!frame.thisp) {
             ok = JS_FALSE;
             goto out2;
diff --git a/js/src/jsobj.cpp b/js/src/jsobj.cpp
index 93855738147b..9e586328c7a6 100644
--- a/js/src/jsobj.cpp
+++ b/js/src/jsobj.cpp
@@ -169,7 +169,6 @@ obj_getSlot(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
     uintN attrs;
     JSObject *pobj;
     JSClass *clasp;
-    JSExtendedClass *xclasp;
 
     slot = (uint32) JSVAL_TO_INT(id);
     if (id == INT_TO_JSVAL(JSSLOT_PROTO)) {
@@ -190,14 +189,11 @@ obj_getSlot(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
         if (clasp == &js_CallClass || clasp == &js_BlockClass) {
             /* Censor activations and lexical scopes per ECMA-262. */
             *vp = JSVAL_NULL;
-        } else if (clasp->flags & JSCLASS_IS_EXTENDED) {
-            xclasp = (JSExtendedClass *) clasp;
-            if (xclasp->outerObject) {
-                pobj = xclasp->outerObject(cx, pobj);
-                if (!pobj)
-                    return JS_FALSE;
-                *vp = OBJECT_TO_JSVAL(pobj);
-            }
+        } else if (pobj->map->ops->thisObject) {
+            pobj = pobj->map->ops->thisObject(cx, pobj);
+            if (!pobj)
+                return JS_FALSE;
+            *vp = OBJECT_TO_JSVAL(pobj);
         }
     }
     return JS_TRUE;
diff --git a/js/src/xpconnect/src/xpcwrappednativejsops.cpp b/js/src/xpconnect/src/xpcwrappednativejsops.cpp
index 8ff110098713..4d3619f1853b 100644
--- a/js/src/xpconnect/src/xpcwrappednativejsops.cpp
+++ b/js/src/xpconnect/src/xpcwrappednativejsops.cpp
@@ -1320,6 +1320,10 @@ XPC_WN_JSOp_ThisObject(JSContext *cx, JSObject *obj)
     if(!XPCPerThreadData::IsMainThread(cx))
         return obj;
 
+    OBJ_TO_OUTER_OBJECT(cx, obj);
+    if(!obj)
+        return nsnull;
+
     JSObject *scope = JS_GetScopeChain(cx);
     if(!scope)
     {