diff --git a/include/MqttSettings.h b/include/MqttSettings.h
index 41b0e6e..f318553 100644
--- a/include/MqttSettings.h
+++ b/include/MqttSettings.h
@@ -20,7 +20,7 @@ public:
     void unsubscribe(const String& topic);
 
     String getPrefix() const;
-    String getClientId();
+    String getClientId() const;
 
 private:
     void NetworkEvent(network_event event);
diff --git a/src/MqttSettings.cpp b/src/MqttSettings.cpp
index c547e0d..39e76e2 100644
--- a/src/MqttSettings.cpp
+++ b/src/MqttSettings.cpp
@@ -179,7 +179,7 @@ String MqttSettingsClass::getPrefix() const
     return Configuration.get().Mqtt.Topic;
 }
 
-String MqttSettingsClass::getClientId()
+String MqttSettingsClass::getClientId() const
 {
     String clientId = Configuration.get().Mqtt.ClientId;
     if (clientId == "") {