diff --git a/nrf5/modules/machine/timer.c b/nrf5/modules/machine/timer.c
index 1866dfa18e..d9d4cf32e5 100644
--- a/nrf5/modules/machine/timer.c
+++ b/nrf5/modules/machine/timer.c
@@ -137,6 +137,12 @@ STATIC mp_obj_t machine_timer_make_new(const mp_obj_type_t *type, size_t n_args,
         self->callback = args[3].u_obj;
     }
 
+#ifdef NRF51
+    self->p_config->irq_priority = 3;
+#else
+    self->p_config->irq_priority = 6;
+#endif
+
     hal_timer_init(self->p_config);
 
     return MP_OBJ_FROM_PTR(self);