pidof -x cannot detect scripts using env

hi, on archlinux with linux-lts kernel, pidof -x doesn't return the expected result as before :

# uname -a
Linux archlive 4.1.16-1-lts #1 SMP Sat Jan 23 07:11:05 CET 2016 x86_64 GNU/Linux
# cat /tmp/pidof-x 
#!/usr/bin/env bash
while :
do
	echo $$
	sleep 10s
done
# ps ax | grep bash
...
 6677 pts/3    S+     0:00 bash /tmp/pidof-x
 6679 pts/4    S+     0:00 bash /tmp/pidof-x
 6681 pts/5    S+     0:00 bash /tmp/pidof-x
 6686 pts/0    S+     0:00 grep --color=auto bash
# pidof -x pidof-x
# pidof -x /tmp/pidof-x
#