How to stop a master?

I followed the work stealing example frm the Well-Typed blog.

I did not use "terminateAllSlaves", so that I can repeatedly run my master "main" function and get slaves to do multiple rounds of work.

However, I cannot do the same from a single GHCi session.

It looks like "startMaster" can only be called once per GHCi, and successive calls block.

Is that correct? Why is that? How can I "stop" a master, so that I can use "startMaster" from GHCi multiple times?