diff --git a/sources/newelementwizard.h b/sources/newelementwizard.h
index 95f239ef8..bfe59f58b 100644
--- a/sources/newelementwizard.h
+++ b/sources/newelementwizard.h
@@ -41,7 +41,7 @@ class NewElementWizard : public QWizard
 	
 		// constructors, destructor
 	public:
-		NewElementWizard(QWidget * = nullptr, Qt::WindowFlags = nullptr);
+		NewElementWizard(QWidget * = nullptr, Qt::WindowFlags = Qt::Widget);
 		~NewElementWizard() override;
 
 		void preselectedLocation(const ElementsLocation &location);
diff --git a/sources/qetmainwindow.h b/sources/qetmainwindow.h
index 890d542ab..033574401 100644
--- a/sources/qetmainwindow.h
+++ b/sources/qetmainwindow.h
@@ -28,7 +28,7 @@ class QETMainWindow : public QMainWindow {
 	
 	// constructor, destructor
 	public:
-	QETMainWindow(QWidget * = nullptr, Qt::WindowFlags = nullptr);
+	QETMainWindow(QWidget * = nullptr, Qt::WindowFlags = Qt::Widget);
 	~QETMainWindow() override;
 	
 	// methods
diff --git a/sources/qetprintpreviewdialog.h b/sources/qetprintpreviewdialog.h
index 4b60109a3..aa6433172 100644
--- a/sources/qetprintpreviewdialog.h
+++ b/sources/qetprintpreviewdialog.h
@@ -36,7 +36,7 @@ class QETPrintPreviewDialog : public QDialog {
 	
 	// constructors, destructor
 	public:
-	QETPrintPreviewDialog(QETProject *, QPrinter *, QWidget * = nullptr, Qt::WindowFlags = nullptr);
+	QETPrintPreviewDialog(QETProject *, QPrinter *, QWidget * = nullptr, Qt::WindowFlags = Qt::Widget);
 	~QETPrintPreviewDialog() override;
 	private:
 	QETPrintPreviewDialog(const QETPrintPreviewDialog &);