How do I allow pop-ups from local files (file:/// addresses) in Firefox 5?

I've created an HTML file on my local machine that I open using a file:/// address. It includes JavaScript that opens new browser windows using window.open().

When I view this page in Firefox 5, the pop-up blocker blocks the new window. I can't override this behavior; clicking the pop-up blocker "Preferences" shows a menu item "Allow pop-ups for", which has no effect.

How do I allow pop-ups for file:/// addresses开发者_C百科 in Firefox 5?

Add <file> to the allowed list under Preferences/Options -> Content -> Block pop-up windows... Exceptions.

edit: This no longer works, see comments