Tvheadend

What is the correct way of using the icon-tag in the XML?
Currently i am using the following:

<channel id="animalplanet">
    <display-name lang="nl">Animal Planet</display-name>
    <icon src="http://location/animalplanet.png"/>
</channel>

When grabbing the first time with a logo it says the following:

2014-06-16 16:46:18.691 /usr/bin/tv_grab_file: grab /usr/bin/tv_grab_file
2014-06-16 16:46:19.871 /usr/bin/tv_grab_file: grab took 1 seconds
2014-06-16 16:46:20.261 /usr/bin/tv_grab_file: parse took 1 seconds
2014-06-16 16:46:20.261 /usr/bin/tv_grab_file:   channels   tot=  203 new=    0 mod=  203
2014-06-16 16:46:20.261 /usr/bin/tv_grab_file:   brands     tot=    0 new=    0 mod=    0
2014-06-16 16:46:20.261 /usr/bin/tv_grab_file:   seasons    tot=    0 new=    0 mod=    0
2014-06-16 16:46:20.261 /usr/bin/tv_grab_file:   episodes   tot=27409 new=    0 mod=    0
2014-06-16 16:46:20.261 /usr/bin/tv_grab_file:   broadcasts tot=27409 new=    0 mod=    0

But none of the channels are updated with a the URL of the channel.. Does it do some kind of check or something?