Session variable is not sent in Laravel 5

I have a Laravel Application, and something strange is happening related to the session variables. I have a method in a controller that checks some inputs and depending of some conditions it decides if continues or just return back (and right here where is my problem), when I make return redirect()->back() I want so send a variable that is a Json, so briefly I have this:

$msg=json_encode([
     'status' => 'failed',
     'field'=>'mail'
 ]);
return redirect()->back()->with('msg',$msg);

So, it redirects very well, but then in the view I have:

@if ( Session::has('msg') )
   //come stuffs
@endif

But it seems likes the msg variable is not passed. Accodring to the Laravel documentation when one uses redirect back the variables are accesible trough Session

via Chebli Mohamed