diff --git a/include/mainwindow.h b/include/mainwindow.h
index bc27452..ad4572c 100644
--- a/include/mainwindow.h
+++ b/include/mainwindow.h
@@ -101,5 +101,5 @@ private:
     QString gbSymbol;
     QString tbSymbol;
     QString pbSymbol;
-    QString getMbToPrettyString(const int64_t &sizeInMbI64, const int &precisionInt, const bool &useGbBool);
+    QString getMbToPrettyString(const int64_t &sizeInMbI64, const int &precisionInt, const bool &useGbBool) const;
 };
diff --git a/src/mainwindow.cpp b/src/mainwindow.cpp
index 5e0e280..6cea9fc 100644
--- a/src/mainwindow.cpp
+++ b/src/mainwindow.cpp
@@ -1451,7 +1451,7 @@ void MainWindow::on_actionSave_Image_triggered()
     screenshot.save(QFileDialog::getSaveFileName(this, tr("Save Image"), "QDiskInfo_" + deviceNodeLineEdit->text().section('/', -1) + ".png", tr("PNG Files (*.png)")));
 }
 
-QString MainWindow::getMbToPrettyString(const int64_t &sizeInMbI64, const int &precisionInt, const bool &useGbBool)
+QString MainWindow::getMbToPrettyString(const int64_t &sizeInMbI64, const int &precisionInt, const bool &useGbBool) const
 {
     if (!sizeInMbI64)
         return "----";