Good thing to think about, I often forget what you can and can't do in older Pythons. I tried it out in 2.6.6, and it seems to be fine:

$ python
Python 2.6.6 (r266:84292, Oct 12 2012, 14:23:48) 
[GCC 4.4.6 20120305 (Red Hat 4.4.6-4)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> validate = None
>>> validate if validate is not None else 5
5
>>> validate = 6
>>> validate if validate is not None else 5
6