diff --git a/sched/Makefile b/sched/Makefile
index 92989e81253..2d743dfd3bb 100644
--- a/sched/Makefile
+++ b/sched/Makefile
@@ -43,6 +43,7 @@ include timer/Make.defs
 include tls/Make.defs
 include wdog/Make.defs
 include wqueue/Make.defs
+include hrtimer/Make.defs
 
 CFLAGS += ${INCDIR_PREFIX}$(TOPDIR)$(DELIM)sched