diff --git a/src/ems-esp.cpp b/src/ems-esp.cpp
index 13dac5f9e..9784c5ebd 100644
--- a/src/ems-esp.cpp
+++ b/src/ems-esp.cpp
@@ -632,7 +632,7 @@ void publishSensorValues() {
 
 // publish Boiler data via MQTT
 void publishEMSValues_boiler() {
-    const size_t        capacity = JSON_OBJECT_SIZE(36); // must recalculate if more objects addded https://arduinojson.org/v6/assistant/
+    const size_t        capacity = JSON_OBJECT_SIZE(41); // must recalculate if more objects addded https://arduinojson.org/v6/assistant/
     DynamicJsonDocument doc(capacity);
     JsonObject          rootBoiler = doc.to<JsonObject>();