Permanently Excluding Folders from SBT Project

Hello,

Is there a way to permanently exclude folders from an SBT project?

When I exclude a folder via the UI, it works -- the folder no longer is in the Project Tree, and Cmd-Shift-N does not show files from the excluded directory. However, when I quit IntelliJ 13 and restart, the excluded folder gets re-included. What's interesting is that you can see the excluded folder not there in the Project Tree when IntelliJ first starts up, but then after a bit, it appears.

Presumably when IntelliJ starts up, it "syncs" things with the build.sbt file, overwriting the excluded folders setting?

I'm sort of newbie to IntelliJ, so apologies in advance for any poor terminology or theories. :)

Thanks,

Charles