diff --git a/src/JsonHelper.cc b/src/JsonHelper.cc
index 25ae0f5b60797c9346b34bade8e3d8883cc65cbf..9a8bd14df600982137cfbe18d9256eae2fe0d27e 100644
--- a/src/JsonHelper.cc
+++ b/src/JsonHelper.cc
@@ -101,13 +101,13 @@ bool JsonHelper::validateKeyTypes(const QJsonObject& jsonObject, const QStringLi
     return true;
 }
 
-bool JsonHelper::parseEnum(QJsonObject& jsonObject, QStringList& enumStrings, QStringList& enumValues, QString& errorString)
+bool JsonHelper::parseEnum(const QJsonObject& jsonObject, QStringList& enumStrings, QStringList& enumValues, QString& errorString)
 {
     enumStrings = jsonObject.value(_enumStringsJsonKey).toString().split(",", QString::SkipEmptyParts);
     enumValues = jsonObject.value(_enumValuesJsonKey).toString().split(",", QString::SkipEmptyParts);
 
     if (enumStrings.count() != enumValues.count()) {
-        errorString = QString("enum strings/values count mismatch: %1");
+        errorString = QString("enum strings/values count mismatch strings:values %1:%2").arg(enumStrings.count()).arg(enumValues.count());
         return false;
     }
 
diff --git a/src/JsonHelper.h b/src/JsonHelper.h
index adc37658c2d94f98891ce44f061e511b40cb7b11..1a01b05d9620aca265c2b97129583187daae3d67 100644
--- a/src/JsonHelper.h
+++ b/src/JsonHelper.h
@@ -24,7 +24,7 @@ public:
     static bool validateRequiredKeys(const QJsonObject& jsonObject, const QStringList& keys, QString& errorString);
     static bool validateKeyTypes(const QJsonObject& jsonObject, const QStringList& keys, const QList<QJsonValue::Type>& types, QString& errorString);
     static bool toQGeoCoordinate(const QJsonValue& jsonValue, QGeoCoordinate& coordinate, bool altitudeRequired, QString& errorString);
-    static bool parseEnum(QJsonObject& jsonObject, QStringList& enumStrings, QStringList& enumValues, QString& errorString);
+    static bool parseEnum(const QJsonObject& jsonObject, QStringList& enumStrings, QStringList& enumValues, QString& errorString);
 
     static void writeQGeoCoordinate(QJsonValue& jsonValue, const QGeoCoordinate& coordinate, bool writeAltitude);