Soft Tilde does not resolve properly on a custom 404 page

When a user on our site gets a 404 error it executes a custom page as marked in the web.config like this
<error statusCode="404" path="/404.aspx" responseMode="ExecuteURL"/> This works well and maintains the 404 status as opposed to a redirect. The custom error page is within a master page that has a menu used throughout the system. In the menu we use soft tildes (ie. ~/store/front.aspx) resolve to the application root directory.
The menu does use server controls and this works  on the rest of the site, but on the custom 404 page the tilde resolves to the folder of the original request.
For instance, if a user navigates to http://www.oursite.com/store/pizza.aspx,  and there is no pizza.aspx the tilde resolves to the store directory instead of the root directory.

Any ideas?
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