diff --git a/libraries/AP_HAL_ChibiOS/UARTDriver.cpp b/libraries/AP_HAL_ChibiOS/UARTDriver.cpp
index 6649643d84..1611dde679 100644
--- a/libraries/AP_HAL_ChibiOS/UARTDriver.cpp
+++ b/libraries/AP_HAL_ChibiOS/UARTDriver.cpp
@@ -635,7 +635,7 @@ void UARTDriver::set_blocking_writes(bool blocking)
     _blocking_writes = blocking;
 }
 
-bool UARTDriver::tx_pending() { return false; }
+bool UARTDriver::tx_pending() { return _writebuf.available() > 0; }
 
 /* Empty implementations of Stream virtual methods */
 uint32_t UARTDriver::available() {