Weird -c 'vi tw=72' behavior

[Munish Chopra]

In my muttrc, I put the following to limit the number of characters per line to 72:

set editor = "vi -c 'set tw=72'"

When I compose a message in mutt, every time after I hit [enter] after typing in the 
subject, it spits out this:

option, 1: set: no tw option: 'set all' gives all option values
Press Enter to continue:

Where am I going wrong? I ripped the tw=72 thing off someone else's muttrc that was on 
the net, but is it the wrong command to pass?

Thanks for your help.
 
- 
-Munish