diff --git a/Pdf4QtEditor/main.cpp b/Pdf4QtEditor/main.cpp
index 9825250..e21c440 100644
--- a/Pdf4QtEditor/main.cpp
+++ b/Pdf4QtEditor/main.cpp
@@ -40,14 +40,18 @@ int main(int argc, char *argv[])
     QApplication::setApplicationDisplayName(QApplication::translate("Application", "PDF4QT Editor"));
 
     QCommandLineOption noDrm("no-drm", "Disable DRM settings of documents.");
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
     QCommandLineOption lightGui("theme-light", "Use a light theme for the GUI.");
     QCommandLineOption darkGui("theme-dark", "Use a dark theme for the GUI.");
+#endif
 
     QCommandLineParser parser;
     parser.setApplicationDescription(QCoreApplication::applicationName());
     parser.addOption(noDrm);
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
     parser.addOption(lightGui);
     parser.addOption(darkGui);
+#endif
     parser.addHelpOption();
     parser.addVersionOption();
     parser.addPositionalArgument("file", "The PDF file to open.");
@@ -58,6 +62,7 @@ int main(int argc, char *argv[])
         pdf::PDFSecurityHandler::setNoDRMMode();
     }
 
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
     if (parser.isSet(lightGui))
     {
         pdf::PDFWidgetUtils::setDarkTheme(false);
@@ -67,6 +72,7 @@ int main(int argc, char *argv[])
     {
         pdf::PDFWidgetUtils::setDarkTheme(true);
     }
+#endif
 
     QIcon appIcon(":/app-icon.svg");
     QApplication::setWindowIcon(appIcon);
diff --git a/Pdf4QtLibWidgets/sources/pdfwidgetutils.cpp b/Pdf4QtLibWidgets/sources/pdfwidgetutils.cpp
index 67f15d7..2a39184 100644
--- a/Pdf4QtLibWidgets/sources/pdfwidgetutils.cpp
+++ b/Pdf4QtLibWidgets/sources/pdfwidgetutils.cpp
@@ -174,10 +174,12 @@ void PDFWidgetUtils::style(QWidget* widget)
     }
 }
 
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
 void PDFWidgetUtils::setDarkTheme(bool isDarkTheme)
 {
     QApplication::styleHints()->setColorScheme(isDarkTheme ? Qt::ColorScheme::Dark : Qt::ColorScheme::Light);
 }
+#endif
 
 bool PDFWidgetUtils::isDarkTheme()
 {
diff --git a/Pdf4QtLibWidgets/sources/pdfwidgetutils.h b/Pdf4QtLibWidgets/sources/pdfwidgetutils.h
index bfa296e..7ac120c 100644
--- a/Pdf4QtLibWidgets/sources/pdfwidgetutils.h
+++ b/Pdf4QtLibWidgets/sources/pdfwidgetutils.h
@@ -60,8 +60,10 @@ public:
     /// Apply style to the widget
     static void style(QWidget* widget);
 
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
     /// Overrides automatically detected dark theme / light theme settings
     static void setDarkTheme(bool isDarkTheme);
+#endif
 
     /// Returns true if the dark theme is currently set for the application.
     static bool isDarkTheme();
diff --git a/Pdf4QtViewer/main.cpp b/Pdf4QtViewer/main.cpp
index a22ef72..1050d8b 100644
--- a/Pdf4QtViewer/main.cpp
+++ b/Pdf4QtViewer/main.cpp
@@ -34,14 +34,18 @@ int main(int argc, char *argv[])
     QApplication::setApplicationDisplayName(QApplication::translate("Application", "PDF4QT Viewer"));
 
     QCommandLineOption noDrm("no-drm", "Disable DRM settings of documents.");
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
     QCommandLineOption lightGui("theme-light", "Use a light theme for the GUI.");
     QCommandLineOption darkGui("theme-dark", "Use a dark theme for the GUI.");
+#endif
 
     QCommandLineParser parser;
     parser.setApplicationDescription(QCoreApplication::applicationName());
     parser.addOption(noDrm);
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
     parser.addOption(lightGui);
     parser.addOption(darkGui);
+#endif
     parser.addHelpOption();
     parser.addVersionOption();
     parser.addPositionalArgument("file", "The PDF file to open.");
@@ -52,6 +56,7 @@ int main(int argc, char *argv[])
         pdf::PDFSecurityHandler::setNoDRMMode();
     }
 
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
     if (parser.isSet(lightGui))
     {
         pdf::PDFWidgetUtils::setDarkTheme(false);
@@ -61,6 +66,7 @@ int main(int argc, char *argv[])
     {
         pdf::PDFWidgetUtils::setDarkTheme(true);
     }
+#endif
 
     QIcon appIcon(":/app-icon.svg");
     QApplication::setWindowIcon(appIcon);