diff --git a/chip/nrf51/clock.c b/chip/nrf51/clock.c
index 4d37de56de..64fd000a51 100644
--- a/chip/nrf51/clock.c
+++ b/chip/nrf51/clock.c
@@ -8,3 +8,9 @@
 void clock_init(void)
 {
 }
+
+int clock_get_freq(void)
+{
+	/* constant 16 MHz clock */
+	return 16000000;
+}