How to Spotlight index a folder under /private/var

I got a directory /private/var/directory that I'd like to index using Spotlight. It looks like everything under /private/var/ is excluded from indexing. I tried to import it using:

mdimport /private/var/directory

But it didn't work. I also thought it might be excluded by some kind of sandboxed environment, but I couldn't figure out if that is the case.

As a last resort I could move the directory somewhere else but I'd rather not do that as it would be a lot of work in this particular case.

How can I force Spotlight to index this directory?