sln2008 does not copy config files to MSTest folder

Several of my tests require settings in my appSettings file to run properly. In my test project, I have an app.config with the following:

<appSettings configSource="appSettings.config"/>

the appSettings.config file is copied into the build folder, but not copied to the location where the tests are run. I end up with the error

ConfigurationErrorsException: Unable to open configSource file 'appSettings.config'

How do I get TeamCity to copy required files to the test folder?