Hi, Last year I've provided a patch that enables DTrace probes under FreeBSD, sadly as it turns out this currently breaks the ability of GHC 8.4.1 to function as a bootstrap compiler under FreeBSD. I've provided a patch that adds a flag to the build system so one can turn off DTrace in case one needs to build a bootstrap compiler. https://phabricator.haskell.org/D4575 This should probably also contain some heads up in the documentation, otherwise someone might end up with a compiler that's not suitable for bootstrapping. Not sure on how this is being handled. I have an idea on how to fix the actual issue but for the time being this might be a suitable workaround. Maybe we can still get this into 8.4.2? I've already notified the FreeBSD ports maintainers regarding this issue. Sorry for the inconvenience. Kind regards, raichoo