Fixed in @aikidosec/firewall 1.7.1, which made the package build cleanly even when `skipLibCheck` is `false`. If your build chokes inside node_modules/@aikidosec on @ts-expect-error lines, upgrade the firewall past 1.7.1. General tip: when a build breaks inside a dependency's .d.ts files, `skipLibCheck: true` in tsconfig is the pragmatic escape hatch, but prefer upgrading the dependency first since the authors usually fix it fast.