Just use helper function in middleware.

app/Http/Middleware/RedirectIfAuthenticated.php

@@ -2,7 +2,6 @@
 
 use Closure;
 use Illuminate\Contracts\Auth\Guard;
-use Illuminate\Http\RedirectResponse;
 
 class RedirectIfAuthenticated
 {
@@ -35,7 +34,7 @@ class RedirectIfAuthenticated
     public function handle($request, Closure $next)
     {
         if ($this->auth->check()) {
-            return new RedirectResponse(url('/home'));
+            return redirect('/home');
         }
 
         return $next($request);