diff --git a/cpu/nrf5x_common/clock.c b/cpu/nrf5x_common/clock.c
index d5686fffbd..3ee5691a53 100644
--- a/cpu/nrf5x_common/clock.c
+++ b/cpu/nrf5x_common/clock.c
@@ -103,10 +103,12 @@ void clock_start_lf(void)
     clock_lf_running = true;
 
     /* calibrate the RC LF clock if applicable */
-#if (CLOCK_HFCLK && (CLOCK_LFCLK == 0))
+#if (CLOCK_LFCLK == CLOCK_LFCLKSRC_SRC_RC)
+    clock_hfxo_request();
     NRF_CLOCK->EVENTS_DONE = 0;
     NRF_CLOCK->TASKS_CAL = 1;
     while (NRF_CLOCK->EVENTS_DONE == 0) {}
+    clock_hfxo_release();
 #endif
 }