diff --git a/examples/opengl/hellowindow/hellowindow.h b/examples/opengl/hellowindow/hellowindow.h
index d4dcbcf3dbe..3934cbf074e 100644
--- a/examples/opengl/hellowindow/hellowindow.h
+++ b/examples/opengl/hellowindow/hellowindow.h
@@ -48,6 +48,9 @@
 **
 ****************************************************************************/
 
+#ifndef HELLOWINDOW_H
+#define HELLOWINDOW_H
+
 #include <QWindow>
 
 #include <QColor>
@@ -117,3 +120,5 @@ private:
     QColor m_color;
     const QSharedPointer<Renderer> m_renderer;
 };
+
+#endif // HELLOWINDOW_H
diff --git a/examples/opengl/openglwindow/openglwindow.h b/examples/opengl/openglwindow/openglwindow.h
index 8db943ddde3..f824c22c9f5 100644
--- a/examples/opengl/openglwindow/openglwindow.h
+++ b/examples/opengl/openglwindow/openglwindow.h
@@ -48,6 +48,9 @@
 **
 ****************************************************************************/
 
+#ifndef OPENGLWINDOW_H
+#define OPENGLWINDOW_H
+
 #include <QWindow>
 #include <QOpenGLFunctions>
 
@@ -89,3 +92,4 @@ private:
 };
 //! [1]
 
+#endif // OPENGLWINDOW_H
diff --git a/examples/opengl/paintedwindow/paintedwindow.h b/examples/opengl/paintedwindow/paintedwindow.h
index 972d8d10bd8..14964e35ff8 100644
--- a/examples/opengl/paintedwindow/paintedwindow.h
+++ b/examples/opengl/paintedwindow/paintedwindow.h
@@ -48,6 +48,9 @@
 **
 ****************************************************************************/
 
+#ifndef PAINTEDWINDOW_H
+#define PAINTEDWINDOW_H
+
 #include <QWindow>
 
 #include <QtGui/qopengl.h>
@@ -102,3 +105,5 @@ private:
     QPropertyAnimation *m_animation;
     QTimer *m_paintTimer;
 };
+
+#endif // PAINTEDWINDOW_H
diff --git a/examples/qpa/windows/window.h b/examples/qpa/windows/window.h
index 438be413b86..1387f4e3bfd 100644
--- a/examples/qpa/windows/window.h
+++ b/examples/qpa/windows/window.h
@@ -48,6 +48,9 @@
 **
 ****************************************************************************/
 
+#ifndef WINDOW_H
+#define WINDOW_H
+
 #include <QWindow>
 #include <QImage>
 
@@ -81,3 +84,5 @@ private:
     QBackingStore *m_backingStore;
     int m_renderTimer;
 };
+
+#endif // WINDOW_H
diff --git a/examples/vulkan/hellovulkantexture/hellovulkantexture.h b/examples/vulkan/hellovulkantexture/hellovulkantexture.h
index a8c96d19870..39cc0387c69 100644
--- a/examples/vulkan/hellovulkantexture/hellovulkantexture.h
+++ b/examples/vulkan/hellovulkantexture/hellovulkantexture.h
@@ -48,6 +48,9 @@
 **
 ****************************************************************************/
 
+#ifndef HELLOVULKANTEXTURE_H
+#define HELLOVULKANTEXTURE_H
+
 #include <QVulkanWindow>
 #include <QImage>
 
@@ -106,3 +109,5 @@ class VulkanWindow : public QVulkanWindow
 public:
     QVulkanWindowRenderer *createRenderer() override;
 };
+
+#endif // HELLOVULKANTEXTURE_H
diff --git a/examples/vulkan/hellovulkanwidget/hellovulkanwidget.h b/examples/vulkan/hellovulkanwidget/hellovulkanwidget.h
index e70d331ae8f..e428c6ae935 100644
--- a/examples/vulkan/hellovulkanwidget/hellovulkanwidget.h
+++ b/examples/vulkan/hellovulkanwidget/hellovulkanwidget.h
@@ -48,6 +48,9 @@
 **
 ****************************************************************************/
 
+#ifndef HELLOVULKANWIDGET_H
+#define HELLOVULKANWIDGET_H
+
 #include "../shared/trianglerenderer.h"
 #include <QWidget>
 
@@ -98,3 +101,5 @@ signals:
     void vulkanInfoReceived(const QString &text);
     void frameQueued(int colorValue);
 };
+
+#endif // HELLOVULKANWIDGET_H
diff --git a/examples/vulkan/hellovulkanwindow/hellovulkanwindow.h b/examples/vulkan/hellovulkanwindow/hellovulkanwindow.h
index 5f52e402cad..7a6db84ae38 100644
--- a/examples/vulkan/hellovulkanwindow/hellovulkanwindow.h
+++ b/examples/vulkan/hellovulkanwindow/hellovulkanwindow.h
@@ -48,6 +48,9 @@
 **
 ****************************************************************************/
 
+#ifndef HELLOVULKANWINDOW_H
+#define HELLOVULKANWINDOW_H
+
 #include <QVulkanWindow>
 
 //! [0]
@@ -75,3 +78,5 @@ public:
     QVulkanWindowRenderer *createRenderer() override;
 };
 //! [0]
+
+#endif // HELLOVULKANWINDOW_H
diff --git a/examples/vulkan/shared/trianglerenderer.h b/examples/vulkan/shared/trianglerenderer.h
index 9a33291a959..bd3daf1d645 100644
--- a/examples/vulkan/shared/trianglerenderer.h
+++ b/examples/vulkan/shared/trianglerenderer.h
@@ -48,6 +48,9 @@
 **
 ****************************************************************************/
 
+#ifndef TRIANGLERENDERER_H
+#define TRIANGLERENDERER_H
+
 #include <QVulkanWindow>
 
 class TriangleRenderer : public QVulkanWindowRenderer
@@ -83,3 +86,5 @@ protected:
     QMatrix4x4 m_proj;
     float m_rotation = 0.0f;
 };
+
+#endif // TRIANGLERENDERER_H
diff --git a/examples/widgets/animation/easing/window.h b/examples/widgets/animation/easing/window.h
index 0c49dd6e8a5..51c7792e190 100644
--- a/examples/widgets/animation/easing/window.h
+++ b/examples/widgets/animation/easing/window.h
@@ -48,6 +48,9 @@
 **
 ****************************************************************************/
 
+#ifndef WINDOW_H
+#define WINDOW_H
+
 #include <QtWidgets>
 
 #include "ui_form.h"
@@ -84,3 +87,5 @@ private:
     Animation *m_anim;
     QSize m_iconSize;
 };
+
+#endif // WINDOW_H
diff --git a/examples/widgets/graphicsview/flowlayout/flowlayout.h b/examples/widgets/graphicsview/flowlayout/flowlayout.h
index 14251072ec5..d8ec2537927 100644
--- a/examples/widgets/graphicsview/flowlayout/flowlayout.h
+++ b/examples/widgets/graphicsview/flowlayout/flowlayout.h
@@ -48,6 +48,9 @@
 **
 ****************************************************************************/
 
+#ifndef FLOWLAYOUT_H
+#define FLOWLAYOUT_H
+
 #include <QGraphicsLayout>
 
 class FlowLayout : public QGraphicsLayout
@@ -84,3 +87,5 @@ inline void FlowLayout::addItem(QGraphicsLayoutItem *item)
 {
     insertItem(-1, item);
 }
+
+#endif // FLOWLAYOUT_H
diff --git a/examples/widgets/graphicsview/flowlayout/window.h b/examples/widgets/graphicsview/flowlayout/window.h
index 24a7cf908b6..9323125fd42 100644
--- a/examples/widgets/graphicsview/flowlayout/window.h
+++ b/examples/widgets/graphicsview/flowlayout/window.h
@@ -48,6 +48,9 @@
 **
 ****************************************************************************/
 
+#ifndef WINDOW_H
+#define WINDOW_H
+
 #include <QGraphicsWidget>
 
 class Window : public QGraphicsWidget
@@ -56,3 +59,5 @@ class Window : public QGraphicsWidget
 public:
     Window(QGraphicsItem *parent = nullptr);
 };
+
+#endif // WINDOW_H
diff --git a/examples/widgets/widgets/validators/validatorwidget.h b/examples/widgets/widgets/validators/validatorwidget.h
index bcc4a9b91e6..7b80c585040 100644
--- a/examples/widgets/widgets/validators/validatorwidget.h
+++ b/examples/widgets/widgets/validators/validatorwidget.h
@@ -48,6 +48,9 @@
 **
 ****************************************************************************/
 
+#ifndef VALIDATORWIDGET_H
+#define VALIDATORWIDGET_H
+
 #include <QWidget>
 
 #include "ui_validators.h"
@@ -62,3 +65,5 @@ private slots:
     void updateValidator();
     void updateDoubleValidator();
 };
+
+#endif // VALIDATORWIDGET_H