augtool fails to update writeable file

augtool fails to update writeable file

I installed Augeas on my CentOS box and am getting unexpected behaviour
from augtool.
To whit,
[root@boxen tmp]# ll
-rw-r--r--. 1 root root 27 Sep 19 11:58 /tmp/my.conf
[root@boxen tmp]# cat /tmp/my.conf
OptionOne no
OptionTwo yes
Now I want to use augtool to change OptionOne from no to yes.
[root@boxen tmp]# augtool set /tmp/my.conf/OptionOne yes
[root@boxen tmp]# augtool save
[root@boxen tmp]# cat my.conf
OptionOne no
OptionTwo yes
augtool is not writing the config change to the file. I'm not seeing any
errors. What am I doing wrong?