diff --git a/src/wlan.cpp b/src/wlan.cpp
index a7703fe..9bb6a8e 100644
--- a/src/wlan.cpp
+++ b/src/wlan.cpp
@@ -38,8 +38,9 @@ void disconnect_mqtt(PubSubClient &client, const char *topic) {
 
 size_t construct_json(float *data, char *buffer, int buffer_size) {
     JsonDocument json;
-    json["temperature"] = data[0];
-    json["humidity"] = data[1];
+    json["co2_concentration"] = data[0];
+    json["temperature"] = data[1];
+    json["humidity"] = data[2];
     size_t payload_size = serializeJson(json, buffer, buffer_size);
     return payload_size;
 }