haskell-process-cabal-build prevents input while it's running

When building projects with haskell-process-cabal-build, emacs refuses to accept any keyboard input while the compilation process is running. I noticed this regression around two weeks ago; I was unable to debug it further, as I'm not good enough at elisp to answer the question "what is blocking and eating all the keyboard events?"

I am running with `haskell-process-type` set to `'stack-ghci`, on haskell-mode 20150907.1230 with emacs 24.5.