[Samba] unix password sync = yes problems

[Bob]

Hey all, 

I'd like to be able to sync up the smbpasswd file with the unix passwd file. 

I've read that I can do this with the option

unix password sync set to yes. 

Here is the part of my relevant smb.conf:

        encrypt passwords = Yes
        passwd program = /usr/bin/passwd %u
        passwd chat = *New*UNIX*password* %n\n *ReType*new*UNIX*password* %n\n
        unix password sync = Yes

What else am I missing? With the above configuration I should be able to change a user's password with smbpasswd and have that same command change the /etc/passwd file at the same time, right? What am I missing?

I've tried that, and it doesn't work. 

Any advice would be greatly appreciated. 

Bob