It was ref'ed on purpose: https://github.com/systemd/systemd/commit/3f573096641cf3d350c8779971c644ca74aab93a build-sys: bump required �httpd version MHD_USE_EPOLL_LINUX_ONLY, MHD_USE_DUAL_STACK are only available in next-but-last release. with other words, we need to get a version update into SLE.