diff --git a/testing/ostest/hrtimer.c b/testing/ostest/hrtimer.c
index 48ed46b99..4cd9eb157 100644
--- a/testing/ostest/hrtimer.c
+++ b/testing/ostest/hrtimer.c
@@ -27,6 +27,7 @@
 #include <nuttx/config.h>
 #include <nuttx/hrtimer.h>
 
+#include <assert.h>
 #include <stdio.h>
 #include <sched.h>
 #include <unistd.h>