Custom page template with two dots before PHP file extension

Hello,
I spend half an hour of my life trying to figure the problem and now I’m a bit surprised because it seems like a found a minor but annoying bug in WP.
1) Create a custom page template like addEvent..php (notice two dots)
2) Create a new page and assign it a newly created template (it will show up)
3) Save the post, check the page – and the page shows default template regardless to what we have just created.
Although the template shows up in a list, it does not work because of two dots in a file name. If we rename it to addEvent.php, then it works like a charm.