[PyMOL] help!

[Sona Vasudevan]

Hi!
 I am getting the following error when I try to set stick transparency of my 
object ligand
 PyMOL>set stick_transparency, ligand, 0.7
Traceback (most recent call last):
File "C:\Program Files\DeLano Scientific\PyMOL/modules\pymol\setting.py", 
line 586, in set
v = (float(value),)
ValueError: invalid literal for float(): ligand
 Can someone tell me what I am doing wrong.
 Thanks!
 Sona