diff --git a/examples/jkqtmathtext_test/testform.h b/examples/jkqtmathtext_test/testform.h
index ccf6d49718..06a9a23083 100644
--- a/examples/jkqtmathtext_test/testform.h
+++ b/examples/jkqtmathtext_test/testform.h
@@ -8,10 +8,11 @@
 #include <QPainter>
 #include <QTreeWidget>
 
-
+QT_BEGIN_NAMESPACE
 namespace Ui {
     class TestForm;
 }
+QT_END_NAMESPACE
 
 class TestForm : public QWidget
 {
diff --git a/examples/mandelbrot/mandelbrotmainwindow.h b/examples/mandelbrot/mandelbrotmainwindow.h
index 800a8a618d..359281f948 100644
--- a/examples/mandelbrot/mandelbrotmainwindow.h
+++ b/examples/mandelbrot/mandelbrotmainwindow.h
@@ -4,9 +4,11 @@
 #include <QMainWindow>
 #include "jkqtplotter/graphs/jkqtpimage.h"
 
+QT_BEGIN_NAMESPACE
 namespace Ui {
 class MandelbrotMainWindow;
 }
+QT_END_NAMESPACE
 
 class MandelbrotMainWindow : public QMainWindow
 {
diff --git a/examples/multiplot/test_multiplot_ui.h b/examples/multiplot/test_multiplot_ui.h
index 217939662c..3cc05942fa 100644
--- a/examples/multiplot/test_multiplot_ui.h
+++ b/examples/multiplot/test_multiplot_ui.h
@@ -5,9 +5,11 @@
 #include "jkqtplotter/jkqtplotter.h"
 #include <QGridLayout>
 
+QT_BEGIN_NAMESPACE
 namespace Ui {
     class TestMultiplotUI;
 }
+QT_END_NAMESPACE
 
 class TestMultiplotUI : public QDialog
 {
diff --git a/examples/styling/test_styling.h b/examples/styling/test_styling.h
index 998dcbf9e1..0c6998f71e 100644
--- a/examples/styling/test_styling.h
+++ b/examples/styling/test_styling.h
@@ -4,9 +4,11 @@
 #include <QMainWindow>
 #include "jkqtplotter/jkqtplotter.h"
 
+QT_BEGIN_NAMESPACE
 namespace Ui {
     class TestStyling;
 }
+QT_END_NAMESPACE
 
 class TestStyling : public QMainWindow
 {
diff --git a/examples/ui/formwithjkqtplotter.h b/examples/ui/formwithjkqtplotter.h
index 5d19c0517e..774bfc3c7a 100644
--- a/examples/ui/formwithjkqtplotter.h
+++ b/examples/ui/formwithjkqtplotter.h
@@ -4,9 +4,11 @@
 #include <QWidget>
 #include "jkqtplotter/graphs/jkqtpparsedfunction.h"
 
+QT_BEGIN_NAMESPACE
 namespace Ui {
     class FormWithJKQTPlotter;
 }
+QT_END_NAMESPACE
 
 class FormWithJKQTPlotter : public QWidget
 {
diff --git a/lib/jkqtplotter/jkqtplotter.h b/lib/jkqtplotter/jkqtplotter.h
index 13e1046c88..1025eaaee9 100644
--- a/lib/jkqtplotter/jkqtplotter.h
+++ b/lib/jkqtplotter/jkqtplotter.h
@@ -1721,6 +1721,8 @@ class JKQTPLOTTER_LIB_EXPORT JKQTPlotter: public QWidget {
 
 };
 
+QT_BEGIN_NAMESPACE
+
 /** \brief qHash-variant used by JKQTPlotter
  *  \internal
  *  \ingroup jkqtpplottersupprt
@@ -1748,4 +1750,6 @@ inline uint qHash(const Qt::KeyboardModifiers &key, uint /*seed*/ ) noexcept(noe
     return static_cast<uint>(key);
 }
 
+QT_END_NAMESPACE
+
 #endif // JKQTPLOTTER_H