diff --git a/src/plugins/platformthemes/gtk3/qgtk3interface.cpp b/src/plugins/platformthemes/gtk3/qgtk3interface.cpp
index d3195863af..4ce7d92ceb 100644
--- a/src/plugins/platformthemes/gtk3/qgtk3interface.cpp
+++ b/src/plugins/platformthemes/gtk3/qgtk3interface.cpp
@@ -400,6 +400,22 @@ const QString QGtk3Interface::themeName() const
     return QLatin1StringView(theme_name);
 }
 
+Qt::Appearance QGtk3Interface::appearanceByColors() const
+{
+    const QColor background = color(widget(QGtkWidget::gtk_Default),
+                                    QGtkColorSource::Background,
+                                    GTK_STATE_FLAG_ACTIVE);
+    const QColor foreground = color(widget(QGtkWidget::gtk_Default),
+                                    QGtkColorSource::Foreground,
+                                    GTK_STATE_FLAG_ACTIVE);
+
+    if (foreground.lightness() > background.lightness())
+        return Qt::Appearance::Dark;
+    if (foreground.lightness() < background.lightness())
+        return Qt::Appearance::Light;
+    return Qt::Appearance::Unknown;
+}
+
 inline constexpr QGtk3Interface::QGtkWidget QGtk3Interface::toWidgetType(QPlatformTheme::Font type)
 {
     switch (type) {
diff --git a/src/plugins/platformthemes/gtk3/qgtk3interface_p.h b/src/plugins/platformthemes/gtk3/qgtk3interface_p.h
index 1a44eed6cb..84119cc638 100644
--- a/src/plugins/platformthemes/gtk3/qgtk3interface_p.h
+++ b/src/plugins/platformthemes/gtk3/qgtk3interface_p.h
@@ -99,6 +99,9 @@ public:
     // Return current GTK theme name
     const QString themeName() const;
 
+    // Derive appearance from default colors
+    Qt::Appearance appearanceByColors() const;
+
     // Convert GTK state to/from string
     static int toGtkState(const QString &state);
     static const QLatin1String fromGtkState(GtkStateFlags state);
diff --git a/src/plugins/platformthemes/gtk3/qgtk3storage.cpp b/src/plugins/platformthemes/gtk3/qgtk3storage.cpp
index 8c56d88898..de0fea4139 100644
--- a/src/plugins/platformthemes/gtk3/qgtk3storage.cpp
+++ b/src/plugins/platformthemes/gtk3/qgtk3storage.cpp
@@ -222,7 +222,7 @@ void QGtk3Storage::populateMap()
 
     // Derive appearance from theme name
     m_appearance = newThemeName.contains("dark"_L1, Qt::CaseInsensitive)
-                   ? Qt::Appearance::Dark : Qt::Appearance::Light;
+                   ? Qt::Appearance::Dark : m_interface->appearanceByColors();
 
     if (m_themeName.isEmpty()) {
         qCDebug(lcQGtk3Interface) << "GTK theme initialized:" << newThemeName << m_appearance;