diff --git a/src/mqtt/MQTT.cpp b/src/mqtt/MQTT.cpp
index 4c50ff74..41e45e83 100644
--- a/src/mqtt/MQTT.cpp
+++ b/src/mqtt/MQTT.cpp
@@ -356,8 +356,8 @@ String MQTT::downstreamPacketToJson(MeshPacket *mp)
                                 {"payload", msgPayload}};
 
     // serialize and return it
-    std::string jsonStr = jsonObj.dump();
+    static std::string jsonStr = jsonObj.dump();
     DEBUG_MSG("serialized json message: %s\n", jsonStr.c_str());
 
     return jsonStr.c_str();
-}
\ No newline at end of file
+}