Overwrite default nuget.config file

I added in the same place where my .sln file is a nuget.config with this configuration

<packageSources><add key="local repo" value="C:\myproject\nugetRepository" /></packageSources>

and i also have the default nuget.config in appdata/roaming/NuGet with the following configuration

<packageSources><add key="nuget.org" value="https://api.nuget.org/v3/index.json" protocolVersion="3" /></packageSources>

Reading online I understood that having the nuget.config in my root project should overwrite the default one but, instead when building using MSBuild it always uses the one in appdata!How can i specify to use the one in the root project?