My clean build of origin/master, on 64-bit Linux is showing these failures Unexpected failures: /tmp/ghctest-5_qx1p/test spaces/./pmcheck/should_compile/T11195.run T11195 [exit code non-0] (normal) Unexpected stat failures: /tmp/ghctest-5_qx1p/test spaces/./perf/compiler/T5837.run T5837 [stat too good] (normal) /tmp/ghctest-5_qx1p/test spaces/./perf/compiler/T12234.run T12234 [stat too good] (optasm) (I do wish the summary omitted those long paths; makes it hard to read.) I'm happy about the perf improvements, but why don't they happen for other people? T11195 is a very long-running pattern-match perf test that regularly fails on a heavily loaded machine, with a timeout. It's very tiresome, but I don't think it's a regression. Simon