diff --git a/cores/esp32/HWCDC.cpp b/cores/esp32/HWCDC.cpp
index 25744f0b0a3..6ec8625cff9 100644
--- a/cores/esp32/HWCDC.cpp
+++ b/cores/esp32/HWCDC.cpp
@@ -28,7 +28,7 @@ ESP_EVENT_DEFINE_BASE(ARDUINO_HW_CDC_EVENTS);
 
 static RingbufHandle_t tx_ring_buf = NULL;
 static xQueueHandle rx_queue = NULL;
-static uint8_t rx_data_buf[64];
+static uint8_t rx_data_buf[64] = {0};
 static intr_handle_t intr_handle = NULL;
 static volatile bool initial_empty = false;
 static xSemaphoreHandle tx_lock = NULL;
@@ -195,6 +195,7 @@ void HWCDC::end()
     intr_handle = NULL;
     if(tx_lock != NULL) {
         vSemaphoreDelete(tx_lock);
+        tx_lock = NULL;
     }
     setRxBufferSize(0);
     setTxBufferSize(0);