gmap_location block zoom problem

I have updated to latest HEAD version, I found the 'zoom' option is not working in gmap_location block
I set map macro as follows:

[gmap |id=block0 |control=Small| zoom=8 |width=100% |type=Map|height=200px |behavior=+notype]

however the location block automatically zoom to largest level (i.e. 15). I don't know how to fix that. Any helps would be grateful.