Adding image asset - shortcode generates broken url

Hi there,

When I add an image asset to my article, the following shortcode is generated:

[cms:asset 2641 title="1"]     

but this resolves on the front end with the following image name

/perch/resources/IMAGE-NAME-wautohauto.png

The problem is the "wautohauto" that is added to the end if the filename. It breaks the image url

If I add "width=0 height=0" in the cms to the shortcode, it fixes the error:

[cms:asset 2641 title="1" width=0 height=0]  

What do I have to do so that I dont have to manually add specific width and height values?

Thanks