diff --git a/src/accessors.cc b/src/accessors.cc
index a43eb78b87..45869ea630 100644
--- a/src/accessors.cc
+++ b/src/accessors.cc
@@ -440,10 +440,21 @@ const AccessorDescriptor Accessors::ScriptEvalFromFunctionName = {
 //
 
 
-Handle<Object> Accessors::FunctionGetPrototype(Handle<Object> object) {
-  Isolate* isolate = Isolate::Current();
-  CALL_HEAP_FUNCTION(
-      isolate, Accessors::FunctionGetPrototype(*object, 0), Object);
+Handle<Object> Accessors::FunctionGetPrototype(Handle<JSFunction> function) {
+  CALL_HEAP_FUNCTION(function->GetIsolate(),
+                     Accessors::FunctionGetPrototype(*function, NULL),
+                     Object);
+}
+
+
+Handle<Object> Accessors::FunctionSetPrototype(Handle<JSFunction> function,
+                                               Handle<Object> prototype) {
+  ASSERT(function->should_have_prototype());
+  CALL_HEAP_FUNCTION(function->GetIsolate(),
+                     Accessors::FunctionSetPrototype(*function,
+                                                     *prototype,
+                                                     NULL),
+                     Object);
 }
 
 
@@ -575,10 +586,10 @@ const AccessorDescriptor Accessors::FunctionName = {
 //
 
 
-Handle<Object> Accessors::FunctionGetArguments(Handle<Object> object) {
-  Isolate* isolate = Isolate::Current();
-  CALL_HEAP_FUNCTION(
-      isolate, Accessors::FunctionGetArguments(*object, 0), Object);
+Handle<Object> Accessors::FunctionGetArguments(Handle<JSFunction> function) {
+  CALL_HEAP_FUNCTION(function->GetIsolate(),
+                     Accessors::FunctionGetArguments(*function, NULL),
+                     Object);
 }
 
 
diff --git a/src/accessors.h b/src/accessors.h
index ae56a3d444..38368c2436 100644
--- a/src/accessors.h
+++ b/src/accessors.h
@@ -77,12 +77,10 @@ class Accessors : public AllStatic {
   };
 
   // Accessor functions called directly from the runtime system.
-  static Handle<Object> FunctionGetPrototype(Handle<Object> object);
-  static Handle<Object> FunctionGetArguments(Handle<Object> object);
-
-  MUST_USE_RESULT static MaybeObject* FunctionSetPrototype(JSObject* object,
-                                                      Object* value,
-                                                      void*);
+  static Handle<Object> FunctionSetPrototype(Handle<JSFunction> object,
+                                             Handle<Object> value);
+  static Handle<Object> FunctionGetPrototype(Handle<JSFunction> object);
+  static Handle<Object> FunctionGetArguments(Handle<JSFunction> object);
 
   // Accessor infos.
   static Handle<AccessorInfo> MakeModuleExport(
@@ -90,13 +88,13 @@ class Accessors : public AllStatic {
 
  private:
   // Accessor functions only used through the descriptor.
+  static MaybeObject* FunctionSetPrototype(JSObject* object, Object*, void*);
   static MaybeObject* FunctionGetPrototype(Object* object, void*);
   static MaybeObject* FunctionGetLength(Object* object, void*);
   static MaybeObject* FunctionGetName(Object* object, void*);
   static MaybeObject* FunctionGetArguments(Object* object, void*);
   static MaybeObject* FunctionGetCaller(Object* object, void*);
-  MUST_USE_RESULT static MaybeObject* ArraySetLength(JSObject* object,
-                                                     Object* value, void*);
+  static MaybeObject* ArraySetLength(JSObject* object, Object*, void*);
   static MaybeObject* ArrayGetLength(Object* object, void*);
   static MaybeObject* StringGetLength(Object* object, void*);
   static MaybeObject* ScriptGetName(Object* object, void*);
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index 2a385aa486..82b2320c6b 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -491,7 +491,7 @@ Handle<JSFunction> Genesis::CreateEmptyFunction(Isolate* isolate) {
     // prototype, otherwise the missing initial_array_prototype will cause
     // assertions during startup.
     native_context()->set_initial_array_prototype(*prototype);
-    SetPrototype(object_fun, prototype);
+    Accessors::FunctionSetPrototype(object_fun, prototype);
   }
 
   // Allocate the empty function as the prototype for function ECMAScript
@@ -1632,7 +1632,7 @@ Handle<JSFunction> Genesis::InstallInternalArray(
                       true, true);
   Handle<JSObject> prototype =
       factory()->NewJSObject(isolate()->object_function(), TENURED);
-  SetPrototype(array_function, prototype);
+  Accessors::FunctionSetPrototype(array_function, prototype);
 
   InternalArrayConstructorStub internal_array_constructor_stub(isolate());
   Handle<Code> code = internal_array_constructor_stub.GetCode(isolate());
@@ -1730,7 +1730,7 @@ bool Genesis::InstallNatives() {
                         Builtins::kIllegal, false, false);
     Handle<JSObject> prototype =
         factory()->NewJSObject(isolate()->object_function(), TENURED);
-    SetPrototype(script_fun, prototype);
+    Accessors::FunctionSetPrototype(script_fun, prototype);
     native_context()->set_script_function(*script_fun);
 
     Handle<Map> script_map = Handle<Map>(script_fun->initial_map());
@@ -1886,7 +1886,7 @@ bool Genesis::InstallNatives() {
                         Builtins::kIllegal, false, false);
     Handle<JSObject> prototype =
         factory()->NewJSObject(isolate()->object_function(), TENURED);
-    SetPrototype(opaque_reference_fun, prototype);
+    Accessors::FunctionSetPrototype(opaque_reference_fun, prototype);
     native_context()->set_opaque_reference_function(*opaque_reference_fun);
   }
 
diff --git a/src/handles.cc b/src/handles.cc
index 48114d91a7..b173edc991 100644
--- a/src/handles.cc
+++ b/src/handles.cc
@@ -208,17 +208,6 @@ Handle<String> FlattenGetString(Handle<String> string) {
 }
 
 
-Handle<Object> SetPrototype(Handle<JSFunction> function,
-                            Handle<Object> prototype) {
-  ASSERT(function->should_have_prototype());
-  CALL_HEAP_FUNCTION(function->GetIsolate(),
-                     Accessors::FunctionSetPrototype(*function,
-                                                     *prototype,
-                                                     NULL),
-                     Object);
-}
-
-
 Handle<Object> SetProperty(Isolate* isolate,
                            Handle<Object> object,
                            Handle<Object> key,
diff --git a/src/handles.h b/src/handles.h
index 90db7d1212..560944cc14 100644
--- a/src/handles.h
+++ b/src/handles.h
@@ -322,9 +322,6 @@ Handle<JSGlobalProxy> ReinitializeJSGlobalProxy(
     Handle<JSFunction> constructor,
     Handle<JSGlobalProxy> global);
 
-Handle<Object> SetPrototype(Handle<JSFunction> function,
-                            Handle<Object> prototype);
-
 Handle<ObjectHashSet> ObjectHashSetAdd(Handle<ObjectHashSet> table,
                                        Handle<Object> key);
 
diff --git a/src/ic.cc b/src/ic.cc
index 3c22580c2c..ad1a313376 100644
--- a/src/ic.cc
+++ b/src/ic.cc
@@ -925,7 +925,7 @@ MaybeObject* LoadIC::Load(State state,
         if (FLAG_trace_ic) PrintF("[LoadIC : +#prototype /function]\n");
 #endif
       }
-      return *Accessors::FunctionGetPrototype(object);
+      return *Accessors::FunctionGetPrototype(Handle<JSFunction>::cast(object));
     }
   }
 
diff --git a/src/runtime.cc b/src/runtime.cc
index 655304470b..f6da37176b 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -2780,16 +2780,13 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_FunctionSetLength) {
 
 
 RUNTIME_FUNCTION(MaybeObject*, Runtime_FunctionSetPrototype) {
-  SealHandleScope shs(isolate);
+  HandleScope scope(isolate);
   ASSERT(args.length() == 2);
 
-  CONVERT_ARG_CHECKED(JSFunction, fun, 0);
+  CONVERT_ARG_HANDLE_CHECKED(JSFunction, fun, 0);
+  CONVERT_ARG_HANDLE_CHECKED(Object, value, 1);
   ASSERT(fun->should_have_prototype());
-  Object* obj;
-  { MaybeObject* maybe_obj =
-        Accessors::FunctionSetPrototype(fun, args[1], NULL);
-    if (!maybe_obj->ToObject(&obj)) return maybe_obj;
-  }
+  Accessors::FunctionSetPrototype(fun, value);
   return args[0];  // return TOS
 }