gitk fails to parse git log output in 1.5.3

gitk shows an error "Can't parse git log output: {\x1b[33commit..." at
startup and quits.

Obviously it's because my git-log outputs in color mode. But the same
happens (and git-log still outputs in colors) after I set color.pager=false. 

What am I missing?

Thanks.
-- 
Jing Xue