diff --git a/src/mqtt.cpp b/src/mqtt.cpp
index 9196b95e3..cbb569f28 100644
--- a/src/mqtt.cpp
+++ b/src/mqtt.cpp
@@ -695,7 +695,7 @@ void Mqtt::register_mqtt_ha_binary_sensor(const __FlashStringHelper * name, cons
         return;
     }
 
-    StaticJsonDocument<EMSESP_MAX_JSON_SIZE_SMALL> doc;
+    StaticJsonDocument<EMSESP_MAX_JSON_SIZE_HA_CONFIG> doc;
 
     doc["name"]    = name;
     doc["uniq_id"] = entity;