$ nix-build -A tarball --check
checking path(s) ‘/nix/store/85k0lfp0dqza0yny0b8ljnhwg7jsnmy5-9c7029ef3b9301c9faf55659ea281332f5f6a281.tar.gz’

trying https://github.com/johbo/reproduce-nix-unicode-darwin/archive/9c7029ef3b9301c9faf55659ea281332f5f6a281.tar.gz
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                Dload  Upload   Total   Spent    Left  Speed
100   176    0   176    0     0    176      0 --:--:-- --:--:-- --:--:--   301
100   501  100   501    0     0    501      0  0:00:01  0:00:01 --:--:--   702
unpacking source archive /private/var/folders/v2/kx2sg5693tb1h84zc2hmjjgr0000gn/T/nix-build-9c7029ef3b9301c9faf55659ea281332f5f6a281.tar.gz.drv-0/9c7029ef3b9301c9faf55659ea281332f5f6a281.tar.gz
warning: rewriting hashes in ‘/nix/store/85k0lfp0dqza0yny0b8ljnhwg7jsnmy5-9c7029ef3b9301c9faf55659ea281332f5f6a281.tar.gz’; cross fingers
/nix/store/85k0lfp0dqza0yny0b8ljnhwg7jsnmy5-9c7029ef3b9301c9faf55659ea281332f5f6a281.tar.gz

$ nix-build -A tarball
these derivations will be built:
  /nix/store/idpgvqqr2ybc4yljz2gxaqnaa2gqphvj-source.drv
building path(s) ‘/nix/store/py8mvgb52sng8xa99s7dnmnhbifh0vid-source’

trying https://github.com/johbo/reproduce-nix-unicode-darwin/archive/9c7029ef3b9301c9faf55659ea281332f5f6a281.tar.gz
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                Dload  Upload   Total   Spent    Left  Speed
100   176    0   176    0     0    176      0 --:--:-- --:--:-- --:--:--   216
100   501    0   501    0     0    501      0 --:--:--  0:00:01 --:--:--   501
unpacking source archive /tmp/nix-build-source.drv-0/9c7029ef3b9301c9faf55659ea281332f5f6a281.tar.gz
output path ‘/nix/store/py8mvgb52sng8xa99s7dnmnhbifh0vid-source’ has r:sha256 hash ‘0izvp8n1mby460w4ylpmicg1j4jla722vjk8psflizqjn9xl26jc’ when ‘1h7z2wax8ywhp0zr08qm78573rcd6nq3y8scl5pbv3lhpilf44sr’ was expected
error: build of ‘/nix/store/idpgvqqr2ybc4yljz2gxaqnaa2gqphvj-source.drv’ failed