Project dependencies in a nuget package are being copied to the application bin folder despite being marked PrivateAssets

I have .netcore2.0 app called MyHelper.MyHelper is referencing a .netstandard2.0 project called B.MyHelper is published as a nuget package.

I need to use MyHelper in other projects and solutions only at build time, therefore in my other projects I mark this nuget package as private:

<PackageReference Include="MyHelper" Version="1.0.0"><PrivateAssets>all</PrivateAssets></PackageReference>

However in the output folder of my other projects consuming this nuget package, B.dll is being present.I do not want that, as it is meant to be only for build time.How do I stop it from being shipped to the applications.Thanks