The name 'AutomationId' does not exist in the current context

I have assembly with UI automation tests (White).

I've introduced a class with all Autination Id's to be reused in this assembly:

public static class AutomationId
{
    public static class Toolbar
    {
        public const string MyControl = "MyControlId";
    }
}

And now i'm trying to use it in my test class (the same assembly):

var control = mainWindow.Get<Button>(AutomationId.Toolbar.MyControl);

This code can be compiled locally. But on TeamCity I'm getting a such error:

The name 'AutomationId' does not exist in the current context