diff --git a/variants/ARDUINO_NANO33BLE/conf/mbed_app.json b/variants/ARDUINO_NANO33BLE/conf/mbed_app.json
index 279ca8808..3f72f4c38 100644
--- a/variants/ARDUINO_NANO33BLE/conf/mbed_app.json
+++ b/variants/ARDUINO_NANO33BLE/conf/mbed_app.json
@@ -5,6 +5,7 @@
   ],
   "target_overrides": {
     "*": {
+      "target.lf_clock_src":"NRF_LF_SRC_SYNTH",
       "target.printf_lib": "std",
       "platform.stdio-buffered-serial": false,
       "platform.stdio-baud-rate": 115200,
diff --git a/variants/ARDUINO_NANO33BLE/variant.cpp b/variants/ARDUINO_NANO33BLE/variant.cpp
index c92e42eda..c31d4e583 100644
--- a/variants/ARDUINO_NANO33BLE/variant.cpp
+++ b/variants/ARDUINO_NANO33BLE/variant.cpp
@@ -135,12 +135,18 @@ extern "C" {
 #include "nrf_rtc.h"
 #include "nrf_uarte.h"
 #include "nrf_uart.h"
+#include "nrf_clock.h"
 
 void initVariant() {
   // turn power LED on
   pinMode(LED_PWR, OUTPUT);
   digitalWrite(LED_PWR, HIGH);
 
+  if (nrf_clock_int_enable_check(NRF_CLOCK_INT_LF_STARTED_MASK)) {
+    // NINA B306 01B modules (without 32k xtal)
+    nrf_clock_int_disable(NRF_CLOCK_INT_LF_STARTED_MASK);
+  }
+
   // Errata Nano33BLE - I2C pullup is controlled by the SWO pin.
   // Configure the TRACEMUX to disable routing SWO signal to pin.
   NRF_CLOCK->TRACECONFIG = 0;
@@ -159,10 +165,12 @@ void initVariant() {
   digitalWrite(PIN_ENABLE_I2C_PULLUP, HIGH);
 
   // Disable UARTE0 which is initially enabled by the bootloader
-  nrf_uarte_task_trigger(NRF_UARTE0, NRF_UARTE_TASK_STOPRX); 
-  while (!nrf_uarte_event_check(NRF_UARTE0, NRF_UARTE_EVENT_RXTO)) ; 
-  NRF_UARTE0->ENABLE = 0; 
-  NRF_UART0->ENABLE = 0; 
+  if (nrf_uarte_event_check(NRF_UARTE0, NRF_UARTE_EVENT_RXTO)) {
+    nrf_uarte_task_trigger(NRF_UARTE0, NRF_UARTE_TASK_STOPRX);
+    while (!nrf_uarte_event_check(NRF_UARTE0, NRF_UARTE_EVENT_RXTO));
+    NRF_UARTE0->ENABLE = 0;
+    NRF_UART0->ENABLE = 0;
+  }
 
   NRF_PWM_Type* PWM[] = {
     NRF_PWM0, NRF_PWM1, NRF_PWM2