fatal error: systemd/sd-bus.h

Hi Just trying to compile on gentoo linux... getting error:

../clients/keyboard.c:44:10: fatal error: systemd/sd-bus.h: No such file or directory
 #include <systemd/sd-bus.h>
          ^~~~~~~~~~~~~~~~~~
compilation terminated.
ninja: build stopped: subcommand failed.

On gentoo we use OpenRC, not systemd... is this the problem?