diff --git a/src/util/externalcommandhelper.h b/src/util/externalcommandhelper.h
--- a/src/util/externalcommandhelper.h
+++ b/src/util/externalcommandhelper.h
@@ -42,8 +42,8 @@
     void quit();
 
 public:
-    bool readData(const QString& sourceDevice, QByteArray& buffer, qint64 offset, qint64 size);
-    bool writeData(const QString& targetDevice, const QByteArray& buffer, qint64 offset);
+    bool readData(const QString& sourceDevice, QByteArray& buffer, const qint64 offset, const qint64 size);
+    bool writeData(const QString& targetDevice, const QByteArray& buffer, const qint64 offset);
 
 public Q_SLOTS:
     ActionReply init(const QVariantMap& args);
diff --git a/src/util/externalcommandhelper.cpp b/src/util/externalcommandhelper.cpp
--- a/src/util/externalcommandhelper.cpp
+++ b/src/util/externalcommandhelper.cpp
@@ -102,7 +102,7 @@
     @param size the number of bytes to read
     @return true on success
 */
-bool ExternalCommandHelper::readData(const QString& sourceDevice, QByteArray& buffer, qint64 offset, qint64 size)
+bool ExternalCommandHelper::readData(const QString& sourceDevice, QByteArray& buffer, const qint64 offset, const qint64 size)
 {
     QFile device(sourceDevice);
 
@@ -132,7 +132,7 @@
     @param offset offset where to begin writing
     @return true on success
 */
-bool ExternalCommandHelper::writeData(const QString &targetDevice, const QByteArray& buffer, qint64 offset)
+bool ExternalCommandHelper::writeData(const QString &targetDevice, const QByteArray& buffer, const qint64 offset)
 {
     QFile device(targetDevice);
     if (!device.open(QIODevice::WriteOnly | QIODevice::Append | QIODevice::Unbuffered)) {