diff --git a/src/shared/mkdir.h b/src/shared/mkdir.h
index d15ede60646..dd5b41ec6f4 100644
--- a/src/shared/mkdir.h
+++ b/src/shared/mkdir.h
@@ -22,6 +22,7 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+#include <stdbool.h>
 #include <sys/types.h>
 
 int mkdir_safe(const char *path, mode_t mode, uid_t uid, gid_t gid);