Static index.html file not recognized anymore

Since upgrading to the 2.3.x (as far as I’ve noticed), I can’t upload a static index.html file and have it show up in the browser — what happens is that a WordPress “not found” page comes up, instead of the index.html file I uploaded.

I use this to deflect visitors while I’m upgrading WP so that they won’t see possible errors and whatnot while new files are in transit, but getting deflected to WP’s 404 page doesn’t help this one bit.

I’m thinking it might have something to with the htaccess/permalinks stuff that WP has, but I’m not entirely sure. I haven’t messed with the htaccess file other than add a few lines for disabling hotlinking.