diff --git a/CHANGES.rst b/CHANGES.rst
index a7ff14f..8882065 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -17,6 +17,7 @@ in-progress
 - Improve firmwares :ref:`node-wifi-mqtt-homie` and :ref:`node-wifi-mqtt-homie-battery`
 - :ref:`node-wifi-mqtt`: Fix JSON serialization: Transmit sensor readings as float values. Thanks, Matthias!
 - :ref:`node-wifi-mqtt`: Improve configuration and documentation
+- :ref:`node-wifi-mqtt`: Fix JSON serialization again, there was an off-by-one-error. Thanks, Giuseppe!
 
 
 2017-03-17 0.13.0
diff --git a/node-wifi-mqtt/node-wifi-mqtt.ino b/node-wifi-mqtt/node-wifi-mqtt.ino
index bddbf19..7b988c1 100644
--- a/node-wifi-mqtt/node-wifi-mqtt.ino
+++ b/node-wifi-mqtt/node-wifi-mqtt.ino
@@ -365,9 +365,8 @@ void loop() {
   getHumidityTemperature();
 
 
-  // Prepare data, build JSON object
-
-  StaticJsonBuffer<256> jsonBuffer;
+  // Build JSON object containing sensor readings
+  StaticJsonBuffer<512> jsonBuffer;
 
   JsonObject& root = jsonBuffer.createObject();
   root["weight"]                    = String(weightChar).toFloat();
@@ -384,7 +383,8 @@ void loop() {
 
 
   // Serialize data
-  char payload[256];
+  int json_length = root.measureLength();
+  char payload[json_length+1];
   root.printTo(payload, sizeof(payload));