Thunar 4.18.0 - Can't set custom window size

The new updated Thunar opens as a big rectangular window on my archlinux setup. To make sure Thunar always opens as a cute, "square" window, I had this rule in devilspie2 for years:

if string.match(get_window_name(), "Thunar") then set_window_size (720, 540); end

It's been working great for years! But now, after yesterday's update to Xfce 4.18, Thunar seems to ignore my custom window size settings. It keeps resetting itself to a big rectangular window of 1074x511px in size.

EDIT: My previous version of Thunar (before this last update) was 4.16.11-2