VisualStudio 2015 strange "Error"

I'm seeing a strange error after upgrade to the release version of Visual Studio 2015 Enterprise.

I have a line of code that looks like this (objConfig is of type Functions.Config and both dBUtils and Config are defined in classes in app_code):

Functions.dBUtils objDB = new Functions.dBUtils("[dbConnectionString]", objConfig);

Visual Studio 2015 is putting a red, wavy underline under Functions.dBUtils and is telling me that "The type 'Config' is defined in an assembly that is not referenced. You must add a reference to assembly 'App_SubCode_EntityUtils.bmfq2tcs, Version=0.0.0.0, Culture=neurtal, PublicKeyToken=null"

Visual Studio 2013 did not show this "error" and Visual Studio 2015 shows the error but at the same time compiles the page/site without any compiler errors and the site runs and debugs fine.

Thoughts?

TIA