This issue is already fixed upstream, but we are using v3.0.0 which doesn't include the fix. https://github.com/yaoweibin/nginx_upstream_check_module/commit/2a52fbf565d0d5bdc9f25382b5af6e952216831f
Fixed: https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=b5ba1ddb6b1eb7fb418d9e8f268fae2dd06d44d2 I
I didn't bother with a revbump since 1.10.0 is pretty new, the fix is trivial, and it seems like nobody else is using this module anyway (or else they would have complained by now).