diff --git a/Adafruit_MQTT.cpp b/Adafruit_MQTT.cpp
index eaaff81..752e252 100644
--- a/Adafruit_MQTT.cpp
+++ b/Adafruit_MQTT.cpp
@@ -782,7 +782,7 @@ uint16_t Adafruit_MQTT::publishPacket(uint8_t *packet, const char *topic,
   len += bLen; // remaining len excludes header byte & length field
 
   // Now you can start generating the packet!
-  p[0] = MQTT_CTRL_PUBLISH << 4 | qos << 1;
+  p[0] = MQTT_CTRL_PUBLISH << 4 | qos << 1 | (retain ? 1 : 0);
   p++;
 
   // fill in packet[1] last