diff --git a/libraries/GCS_MAVLink/GCS_MAVLink.cpp b/libraries/GCS_MAVLink/GCS_MAVLink.cpp
index 436a26f5f6..c4f531822d 100644
--- a/libraries/GCS_MAVLink/GCS_MAVLink.cpp
+++ b/libraries/GCS_MAVLink/GCS_MAVLink.cpp
@@ -140,7 +140,7 @@ void comm_send_buffer(mavlink_channel_t chan, const uint8_t *buf, uint8_t len)
     }
     const size_t written = mavlink_comm_port[chan]->write(buf, len);
 #if CONFIG_HAL_BOARD == HAL_BOARD_SITL
-    if (written < len) {
+    if (written < len && !mavlink_comm_port[chan]->is_write_locked()) {
         AP_HAL::panic("Short write on UART: %lu < %u", (unsigned long)written, len);
     }
 #else