--- a/js/src/jsiter.cpp
+++ b/js/src/jsiter.cpp
@@ -1537,17 +1537,17 @@ typedef enum JSGeneratorOp {
 } JSGeneratorOp;
 
 /*
  * Start newborn or restart yielding generator and perform the requested
  * operation inside its frame.
  */
 static JSBool
 SendToGenerator(JSContext *cx, JSGeneratorOp op, HandleObject obj,
-                JSGenerator *gen, const Value &arg)
+                JSGenerator *gen, HandleValue arg)
 {
     if (gen->state == JSGEN_RUNNING || gen->state == JSGEN_CLOSING) {
         JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL, JSMSG_NESTING_GENERATOR);
         return false;
     }
 
     JSGeneratorState futureState;
     JS_ASSERT(gen->state == JSGEN_NEWBORN || gen->state == JSGEN_OPEN);
@@ -1623,17 +1623,17 @@ CloseGenerator(JSContext *cx, HandleObje
     if (!gen) {
         /* Generator prototype object. */
         return true;
     }
 
     if (gen->state == JSGEN_CLOSED)
         return true;
 
-    return SendToGenerator(cx, JSGENOP_CLOSE, obj, gen, UndefinedValue());
+    return SendToGenerator(cx, JSGENOP_CLOSE, obj, gen, JS::UndefinedHandleValue);
 }
 
 JS_ALWAYS_INLINE bool
 IsGenerator(const Value &v)
 {
     return v.isObject() && v.toObject().is<GeneratorObject>();
 }
 
@@ -1652,21 +1652,18 @@ generator_send_impl(JSContext *cx, CallA
 
     if (gen->state == JSGEN_NEWBORN && args.hasDefined(0)) {
         RootedValue val(cx, args[0]);
         js_ReportValueError(cx, JSMSG_BAD_GENERATOR_SEND,
                             JSDVG_SEARCH_STACK, val, NullPtr());
         return false;
     }
 
-    if (!SendToGenerator(cx, JSGENOP_SEND, thisObj, gen,
-                         args.length() > 0 ? args[0] : UndefinedValue()))
-    {
+    if (!SendToGenerator(cx, JSGENOP_SEND, thisObj, gen, args.get(0)))
         return false;
-    }
 
     args.rval().set(gen->fp->returnValue());
     return true;
 }
 
 JSBool
 generator_send(JSContext *cx, unsigned argc, Value *vp)
 {
@@ -1682,17 +1679,17 @@ generator_next_impl(JSContext *cx, CallA
     RootedObject thisObj(cx, &args.thisv().toObject());
 
     JSGenerator *gen = thisObj->as<GeneratorObject>().getGenerator();
     if (!gen || gen->state == JSGEN_CLOSED) {
         /* This happens when obj is the generator prototype. See bug 352885. */
         return js_ThrowStopIteration(cx);
     }
 
-    if (!SendToGenerator(cx, JSGENOP_NEXT, thisObj, gen, UndefinedValue()))
+    if (!SendToGenerator(cx, JSGENOP_NEXT, thisObj, gen, JS::UndefinedHandleValue))
         return false;
 
     args.rval().set(gen->fp->returnValue());
     return true;
 }
 
 JSBool
 generator_next(JSContext *cx, unsigned argc, Value *vp)
@@ -1710,21 +1707,18 @@ generator_throw_impl(JSContext *cx, Call
 
     JSGenerator *gen = thisObj->as<GeneratorObject>().getGenerator();
     if (!gen || gen->state == JSGEN_CLOSED) {
         /* This happens when obj is the generator prototype. See bug 352885. */
         cx->setPendingException(args.length() >= 1 ? args[0] : UndefinedValue());
         return false;
     }
 
-    if (!SendToGenerator(cx, JSGENOP_THROW, thisObj, gen,
-                         args.length() > 0 ? args[0] : UndefinedValue()))
-    {
+    if (!SendToGenerator(cx, JSGENOP_THROW, thisObj, gen, args.get(0)))
         return false;
-    }
 
     args.rval().set(gen->fp->returnValue());
     return true;
 }
 
 JSBool
 generator_throw(JSContext *cx, unsigned argc, Value *vp)
 {
@@ -1747,17 +1741,17 @@ generator_close_impl(JSContext *cx, Call
     }
 
     if (gen->state == JSGEN_NEWBORN) {
         SetGeneratorClosed(cx, gen);
         args.rval().setUndefined();
         return true;
     }
 
-    if (!SendToGenerator(cx, JSGENOP_CLOSE, thisObj, gen, UndefinedValue()))
+    if (!SendToGenerator(cx, JSGENOP_CLOSE, thisObj, gen, JS::UndefinedHandleValue))
         return false;
 
     args.rval().set(gen->fp->returnValue());
     return true;
 }
 
 JSBool
 generator_close(JSContext *cx, unsigned argc, Value *vp)