diff --git a/src/paho/mqtt/client.py b/src/paho/mqtt/client.py
index 4ccc8696..58ce2b15 100644
--- a/src/paho/mqtt/client.py
+++ b/src/paho/mqtt/client.py
@@ -3180,6 +3180,10 @@ def _packet_write(self) -> MQTTErrorCode:
                 return MQTTErrorCode.MQTT_ERR_CONN_LOST
 
             if write_length > 0:
+                # Update the last message out time once packet (partial packet) is sent
+                with self._msgtime_mutex:
+                    self._last_msg_out = time_func()
+
                 packet['to_process'] -= write_length
                 packet['pos'] += write_length