Here's the upstream issue: https://github.com/haskell/c2hs/issues/192. This is affecting many projects. The ongoing saga: https://github.com/visq/language-c/issues/39 https://github.com/visq/language-c/issues/43 Not sure if there is a workaround but posting in case anyone else is tripped up by this.