Nbconvert 6.0.7 is including 'Press Ctrl-C again to quit kernel.' when passed --stdout

I’m using nbconvert as part of an integration test for IHaskell, but as of the most recent version it has started including extraneous Jupyter output, i.e. ‘Press Ctrl-C again to quit kernel.’ when passed --stdout. This seems like a regression to me, how would I fix this or work around it?