No stdin after closing SDL program without window manager

Hello all,

I've recently switched from Kubuntu 16.04 to Mint 18 (KDE), and am running 
into the following problem:
When I run an SDL program directly under X without a window manager, and close 
that program, stdin is not returned to the parent process. As an example:

I start X with just an xterm, start MAME (emulator), exit MAME, and return to 
the xterm. My keyboard is simply not working anymore. I can still use the 
mouse to copy/paste into the xterm, but keyboard input is not captured.

I've tested this with several SDL programs, and non-SDL programs, but the 
result is the same: after exiting the SDL program my keyboard doesn't work, 
and after exiting a non-SDL program I have no issue. I also don't have an 
issue when I use a window manager like KDE. I did not have this issue with 
Kubuntu.

Any thoughts on what might cause this issue, and how I might solve it?

Kind regards,

Pieter Hulshoff