NotFoundHttpException - Laravel

i want to make edit-update function.. this is my code :

Admin Controller

  public function edit_ist($id_prog)
{
    $program_studi = ProgramStudi::find($id_prog);
    retu view('edit_ist_program_studi',compact('program_studi'));
}
public function update_ist($id_prog)
{
    $istUpdate = Request::all();
    $program_studi = ProgramStudi::find($id_prog);
    $program_studi->update($istUpdate);
     retu redirect('administrator');
}

Form open in view edit_ist_program_studi

 {{ Form::model($program_studi,['method'=>'PATCH','route'=>['update_prodi',$program_studi->id_prog]])}}

Routes:

Route::patch('admin_page/edit_prodi/{id_prog}',
['as' => 'update_prodi', 'uses' => 'AdminController@update_ist']);

But i found error NotFoundHttpException, can you help me to fix this ? thank you