saving User object fails because of sessionKey

if you modify and try to save a user, you get:

/Library/Ruby/Gems/1.8/gems/parse-ruby-client-0.0.7/lib/parse/client.rb:47:in `request': 105: the sessionToken key is a reserved word (Parse::ParseError)
	from /Library/Ruby/Gems/1.8/gems/parse-ruby-client-0.0.7/lib/parse/object.rb:76:in `save'

in order for it to succeed, you have to first:

    user.delete(Parse::Protocol::KEY_USER_SESSION_TOKEN)