nested master page problem

[prefersgolfing]

I have:
MasterPage.master

Then referencing it as master I have:
AnonymousUser.master and AuthenticatedUser.Master

I have:
Default.aspx and Login.aspx referencing AnonymousUser.master as their master

I have:
Workbench.aspx referencing AuthenticatedUser.Master as it's master.

On Login.aspx, I have DestinationPageURL="~/Workbench.aspx". However, after
the user is authenticated, they are redirected back to Default.aspx. I want
authenticated users to go to Workbench.aspx. I have not tried this
programatically and would like to keep the solution declarative. Any ideas
why it is not redirecting as expected?