NuGet package returns version 4.0.1 while dll version is 4.0.0.0

[ms440]

When I'm using install-package Newtonsoft.Json command in Package Manager Console of VS2010SP1, the package line added to packages.config file in my project says that the version used is 4.0.1, while the assembly in Packages directory - Packages\Newtonsoft.Json.4.0.1\lib\40\Newtonsoft.Json.dll has version number 4.0.0.0.

As a result, I'm getting Error#170 from StructureMap (I'm using SM-2.6.2).