asterisk users - Mar 2008 - iax2 reload does not update channel config for removed key from config file

My previous posts did not seem to make it to the list, so I send it 
again. Apologies if the previous posts ultimately do make it, resulting 
in duplicate posts ...

Version = Asterisk 1.4.18.


Prb:
It looks like that when you remove a key (e.g. username=) from the
iax.conf file, it is not removed from the iax channel configuration 
after a reload. It is only removed if you first define an empty value 
for it, reload the iax configuration, then remove the keyword from the
configuration file and reload again. So it actually updates one way;
from config file to channel configuration, but not the otherway around.
Leaving removed key=value from the configuration file unchanged in the
channel configuration after a reload.

Is this normal behaviour? I could not find any information for it. It
sent me in the wrong directions before I realized what was happening.

rgds,

Hans Feringa