--- a/js/src/jsapi.cpp
+++ b/js/src/jsapi.cpp
@@ -3914,16 +3914,31 @@ JS_CloneFunctionObject(JSContext *cx, Ha
     if (fun->isNative() && IsAsmJSModuleNative(fun->native())) {
         JS_ReportErrorNumber(cx, js_GetErrorMessage, nullptr, JSMSG_CANT_CLONE_OBJECT);
         return nullptr;
     }
 
     return CloneFunctionObject(cx, fun, parent, fun->getAllocKind());
 }
 
+namespace JS {
+
+JS_PUBLIC_API(JSObject *)
+CloneFunctionObject(JSContext *cx, HandleObject funobj, AutoObjectVector &scopeChain)
+{
+    RootedObject dynamicScope(cx);
+    RootedObject unusedStaticScope(cx);
+    if (!CreateScopeObjectsForScopeChain(cx, scopeChain, &dynamicScope, &unusedStaticScope))
+        return nullptr;
+
+    return JS_CloneFunctionObject(cx, funobj, dynamicScope);
+}
+
+} // namespace JS
+
 JS_PUBLIC_API(JSObject *)
 JS_GetFunctionObject(JSFunction *fun)
 {
     return fun;
 }
 
 JS_PUBLIC_API(JSString *)
 JS_GetFunctionId(JSFunction *fun)

--- a/js/src/jsapi.h
+++ b/js/src/jsapi.h
@@ -3529,16 +3529,28 @@ JS_DefineFunctionById(JSContext *cx, JS:
 
 /*
  * Clone a top-level function into a new scope. This function will dynamically
  * fail if funobj was lexically nested inside some other function.
  */
 extern JS_PUBLIC_API(JSObject *)
 JS_CloneFunctionObject(JSContext *cx, JS::Handle<JSObject*> funobj, JS::Handle<JSObject*> parent);
 
+namespace JS {
+
+/*
+ * As above, but providing an explicit scope chain.  scopeChain must not include
+ * the global object on it; that's implicit.  It needs to contain the other
+ * objects that should end up on the clone's scope chain.
+ */
+extern JS_PUBLIC_API(JSObject *)
+CloneFunctionObject(JSContext *cx, HandleObject funobj, AutoObjectVector &scopeChain);
+
+} // namespace JS
+
 /*
  * Given a buffer, return false if the buffer might become a valid
  * javascript statement with the addition of more lines.  Otherwise return
  * true.  The intent is to support interactive compilation - accumulate
  * lines in a buffer until JS_BufferIsCompilableUnit is true, then pass it to
  * the compiler.
  */
 extern JS_PUBLIC_API(bool)