Formula cannot be installed

[nlohmann]

Tapping works:

brew tap wsjcpp/wsjcpp

==> Tapping wsjcpp/wsjcpp
Cloning into '/opt/homebrew/Library/Taps/wsjcpp/homebrew-wsjcpp'...
remote: Enumerating objects: 68, done.
remote: Counting objects: 100% (68/68), done.
remote: Compressing objects: 100% (50/50), done.
remote: Total 68 (delta 29), reused 47 (delta 16), pack-reused 0 (from 0)
Receiving objects: 100% (68/68), 10.00 KiB | 2.00 MiB/s, done.
Resolving deltas: 100% (29/29), done.
Tapped 1 formula (15 files, 18.6KB).

But installing the formula wsjcpp does not:

brew install wsjcpp
Error: wsjcpp/wsjcpp/wsjcpp: undefined method `cellar' for an instance of BottleSpecification