[Newbies] Implementing a simple timer

I'm trying to write a simple timer using a TextMorph and its step method. It should count up every 1 second so I've set stepTime to 1000. My step method looks as follows:

step self time: self time + 1. self contents: self time asString

That should work. But I discover one problem: The timer counts up but it does so way to fast. If I print the numbers onto the Transcript everything works fine. So I think the problem lies within the TextMorph. It seems that during the sent of 'self contents:' the step method is called again so that it is executed long before the stepTime is up.

Am I right with that suspicion? Can anyone think of a way to work around my problem?

Thanks in advance!