Upgrading to 5.1 via Nuget breaks namespaces

Topics: ASP.NET MVC
Feb 6, 2014 at 7:41 PM
Created a new ASP.NET MVC 5 project using VS2013 Update 1 before upgrading the project to 5.1. Using nuget I ran the command:
install-package microsoft.aspnet.mvc -version 5.1.0
This updated the MVC assembly, amongst other things. Once this was done whenever I added new code under a folder say WebApp.Models I would get the red squiggly lines. I tried looking for the main project assembly in object browser but it wasn't listed.

Is this by design?