Resolving TeamCity hosted NuGet packages

We use TeamCIty as a local host of our internal NuGet packages.

We have a project that is exposed via the TeamCity NuGet feed called 'XXX.Core'.

A second project called 'XXX.JobProcessor' uses that feed to resolve the XXX.Core.dll dependencies.

The issues comes when I try to expose the second project ('XXX.JobProcessor') as a NuGet feed

When the build tries to package the NuGet aspect I get an error:

     Unable to find version '1.0.1.0' of package 'XXX.Core'.

It seems that TeamCity can only resolve official NuGet feed dependencies and not it's own feeds.

Having XXX.Core as a ref in the source code is not an option.

Has anyone else come across or am I missing the obvious?

I've attached the nuspec file.