diff --git a/Adafruit_MQTT.h b/Adafruit_MQTT.h
index f093254..b9a4c4a 100644
--- a/Adafruit_MQTT.h
+++ b/Adafruit_MQTT.h
@@ -65,7 +65,9 @@
 #define PING_TIMEOUT_MS 500
 
 // Adjust as necessary, in seconds.  Default to 5 minutes.
-#define MQTT_CONN_KEEPALIVE 300
+#ifndef MQTT_CONN_KEEPALIVE
+  #define MQTT_CONN_KEEPALIVE 300
+#endif
 
 // Largest full packet we're able to send.
 // Need to be able to store at least ~90 chars for a connect packet with full