Dear Cafe, I am getting this when building ghc-8.4.2 from source, with ghc-8.2.2: ghc-8.4.2/libraries/integer-gmp/dist-install/build/libHSinteger-gmp-1.0.2.0_p.a(wrappers.p_o):wrappers.c:function integer_gmp_powm_sec: error: undefined reference to 'mpz_powm_sec' collect2: error: ld returned 1 exit status `gcc' failed in phase `Linker'. (Exit code: 1) make[1]: *** [iserv/ghc.mk:104: iserv/stage2_p/build/tmp/ghc-iserv-prof] Error 1 This may be due to some mis-config on my part, because I'm getting this on one machine only, and it works on others. Still, perhaps you have seen this before, and could help me with an educated guess on what may have caused this. It is especially puzzling because this install of ghc-8.2.2 seems to work perfectly fine for all of my projects. Thanks - J.W.