diff --git a/js/src/js.msg b/js/src/js.msg
index befda7d04182..71fc75458736 100644
--- a/js/src/js.msg
+++ b/js/src/js.msg
@@ -316,7 +316,7 @@ MSG_DEF(JSMSG_SC_RECURSION,           262, 0, JSEXN_INTERNALERR, "recursive obje
 MSG_DEF(JSMSG_CANT_WRAP_XML_OBJECT,   263, 0, JSEXN_TYPEERR, "can't wrap XML objects")
 MSG_DEF(JSMSG_BAD_CLONE_VERSION,      264, 0, JSEXN_ERR, "unsupported structured clone version")
 MSG_DEF(JSMSG_CANT_CLONE_OBJECT,      265, 0, JSEXN_TYPEERR, "can't clone object")
-MSG_DEF(JSMSG_NON_NATIVE_SCOPE,       266, 0, JSEXN_TYPEERR, "non-native scope object")
+MSG_DEF(JSMSG_UNUSED266,              266, 0, JSEXN_NONE, "")
 MSG_DEF(JSMSG_STRICT_FUNCTION_STATEMENT, 267, 0, JSEXN_SYNTAXERR, "in strict mode code, functions may be declared only at top level or immediately within another function")
 MSG_DEF(JSMSG_INVALID_FOR_IN_INIT,    268, 0, JSEXN_SYNTAXERR, "for-in loop let declaration may not have an initializer")
 MSG_DEF(JSMSG_CLEARED_SCOPE,          269, 0, JSEXN_TYPEERR, "attempt to run compile-and-go script on a cleared scope")
diff --git a/js/src/jsinterp.cpp b/js/src/jsinterp.cpp
index 3d7ffd2f7cf7..c5c259a94ec0 100644
--- a/js/src/jsinterp.cpp
+++ b/js/src/jsinterp.cpp
@@ -552,12 +552,14 @@ js::Execute(JSContext *cx, HandleScript script, JSObject &scopeChainArg, Value *
     if (!scopeChain)
         return false;
 
-    /* If we were handed a non-native object, complain bitterly. */
-    if (!scopeChain->isNative()) {
-        JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL, JSMSG_NON_NATIVE_SCOPE);
-        return false;
-    }
-    JS_ASSERT(!scopeChain->getOps()->defineProperty);
+    /* Ensure the scope chain is all same-compartment and terminates in a global. */
+#ifdef DEBUG
+    RawObject s = scopeChain;
+    do {
+        assertSameCompartment(cx, s);
+        JS_ASSERT_IF(!s->enclosingScope(), s->isGlobal());
+    } while ((s = s->enclosingScope()));
+#endif
 
     /* The VAROBJFIX option makes varObj == globalObj in global code. */
     if (!cx->hasRunOption(JSOPTION_VAROBJFIX)) {
diff --git a/js/src/jsinterpinlines.h b/js/src/jsinterpinlines.h
index 2699a0498f10..87df5aefc035 100644
--- a/js/src/jsinterpinlines.h
+++ b/js/src/jsinterpinlines.h
@@ -476,7 +476,6 @@ inline bool
 DefVarOrConstOperation(JSContext *cx, HandleObject varobj, HandlePropertyName dn, unsigned attrs)
 {
     JS_ASSERT(varobj->isVarObj());
-    JS_ASSERT(!varobj->getOps()->defineProperty || varobj->isDebugScope());
 
     RootedShape prop(cx);
     RootedObject obj2(cx);