Rdoc and a class named SM

I’m still on a Ruby 1.8.6 system. rdoc/usage is used together with
getoptlong for providing help to the user.

One of the classes defined in the main module is called SM. This causes
rdoc to spill out an error message “SM is not a class”. Indeed, there is
a module within RDoc of this name.

Of course I could put SM (and the other classes) in their own namespace
(which would be reasonable anyway - I just didn’t do it for laziness,
because the application is so small), so it’s not really a problem. I’m
just curious: Is there maybe a more reasonable way to solve my problem?
Maybe it’s not a good idea to name a class with all-uppercase letters in
the first place?