diff --git a/cpu/nrf5x_common/periph/timer.c b/cpu/nrf5x_common/periph/timer.c
index 556ead9b63..ae944867d5 100644
--- a/cpu/nrf5x_common/periph/timer.c
+++ b/cpu/nrf5x_common/periph/timer.c
@@ -111,7 +111,9 @@ int timer_init(tim_t tim, uint32_t freq, timer_cb_t cb, void *arg)
     }
 
     /* enable interrupts */
-    NVIC_EnableIRQ(timer_config[tim].irqn);
+    if (cb != NULL) {
+        NVIC_EnableIRQ(timer_config[tim].irqn);
+    }
     /* start the timer */
     dev(tim)->TASKS_START = 1;