Before the change closure size is:
$ nix path-info -rsSh $(nix-build --no-link -A kea) | nl | unnix | tail -n 1
131 /<<NIX>>/kea-2.4.0 32.0M 405.6M
After the change:
$ nix path-info -rsSh $(nix-build --no-link -A kea) | nl | unnix | tail -n 1
37 /<<NIX>>/kea-2.4.0 32.0M 246.3M