It seems we forgot to mention in the 7.0.1 release notes that there's a new compile-time flag, --with-rtsopts. From the documentation: 4.16.8. Linker flags to change RTS behaviour GHC lets you exercise rudimentary control over the RTS settings for any given program, by using the -with-rtsopts linker flag. For example, to set -H128m -K1m, link with -with-rtsopts="-H128m -K1m". Cheers, Simon