diff --git a/sys/kern/kern_time.c b/sys/kern/kern_time.c
--- a/sys/kern/kern_time.c
+++ b/sys/kern/kern_time.c
@@ -1183,6 +1183,7 @@
 		NULL, NULL, itimer_init, itimer_fini, UMA_ALIGN_PTR, 0);
 	register_posix_clock(CLOCK_REALTIME,  &rt_clock);
 	register_posix_clock(CLOCK_MONOTONIC, &rt_clock);
+	register_posix_clock(CLOCK_UPTIME, &rt_clock);
 	register_posix_clock(CLOCK_TAI, &rt_clock);
 	p31b_setcfg(CTL_P1003_1B_TIMERS, 200112L);
 	p31b_setcfg(CTL_P1003_1B_DELAYTIMER_MAX, INT_MAX);