diff --git a/ports/nrf/drivers/bluetooth/ble_drv.c b/ports/nrf/drivers/bluetooth/ble_drv.c
index b1caa187d5..1c150b5d71 100644
--- a/ports/nrf/drivers/bluetooth/ble_drv.c
+++ b/ports/nrf/drivers/bluetooth/ble_drv.c
@@ -150,6 +150,13 @@ uint32_t ble_drv_stack_enable(void) {
         .rc_temp_ctiv = 2,
         .accuracy = NRF_CLOCK_LF_ACCURACY_250_PPM
     };
+  #elif BLUETOOTH_LFCLK_SYNTH
+    nrf_clock_lf_cfg_t clock_config = {
+        .source = NRF_CLOCK_LF_SRC_SYNTH,
+        .rc_ctiv = 0,
+        .rc_temp_ctiv = 0,
+        .accuracy = NRF_CLOCK_LF_ACCURACY_50_PPM
+    };
   #else
     nrf_clock_lf_cfg_t clock_config = {
         .source = NRF_CLOCK_LF_SRC_XTAL,
diff --git a/ports/nrf/mphalport.c b/ports/nrf/mphalport.c
index 06c6ba5cc2..a8be2bd6e9 100644
--- a/ports/nrf/mphalport.c
+++ b/ports/nrf/mphalport.c
@@ -55,10 +55,24 @@ void mp_nrf_start_lfclk(void) {
         // Check if the clock was recently stopped but is still running.
         #if USE_WORKAROUND_FOR_ANOMALY_132
         bool was_running = nrf_clock_lf_is_running(NRF_CLOCK);
-        // If so, wait for it to stop. This ensures that the delay for anomaly 132 workaround does
-        // not land us in the middle of the forbidden interval.
+        #endif
+        // If so, wait for it to stop, otherwise the source cannot be changed. This also ensures
+        // that the delay for anomaly 132 workaround does not land us in the middle of the forbidden
+        // interval.
         while (nrf_clock_lf_is_running(NRF_CLOCK)) {
         }
+        // Use the same LFCLK source as for bluetooth so that enabling the softdevice will not cause
+        // an interruption.
+        nrf_clock_lf_src_set(NRF_CLOCK,
+            #if BLUETOOTH_LFCLK_RC
+            NRF_CLOCK_LFCLK_RC
+            #elif BLUETOOTH_LFCLK_SYNTH
+            NRF_CLOCK_LFCLK_Synth
+            #else
+            NRF_CLOCK_LFCLK_Xtal
+            #endif
+            );
+        #if USE_WORKAROUND_FOR_ANOMALY_132
         // If the clock just stopped, we can start it again right away as we are certainly before
         // the forbidden 66-138us interval. Otherwise, apply a delay of 138us to make sure we are
         // after the interval.