diff --git a/libkwineffects/kwineffects.h b/libkwineffects/kwineffects.h
--- a/libkwineffects/kwineffects.h
+++ b/libkwineffects/kwineffects.h
@@ -2091,7 +2091,7 @@
      * a length of 1, on Wayland can be any subset.
      * If the list is empty it means the window is on all desktops
      */
-    QList<int> desktops() const;
+    QVector<int> desktops() const;
 
     int x() const;
     int y() const;
diff --git a/libkwineffects/kwineffects.cpp b/libkwineffects/kwineffects.cpp
--- a/libkwineffects/kwineffects.cpp
+++ b/libkwineffects/kwineffects.cpp
@@ -857,11 +857,7 @@
 WINDOW_HELPER(QStringList, activities, "activities")
 WINDOW_HELPER(bool, skipsCloseAnimation, "skipsCloseAnimation")
 WINDOW_HELPER(KWayland::Server::SurfaceInterface *, surface, "surface")
-
-QList<int> EffectWindow::desktops() const
-{
-    return parent()->property("x11DesktopIds").value<QList<int> >();
-}
+WINDOW_HELPER(QVector<int>, desktops, "x11DesktopIds")
 
 QString EffectWindow::windowClass() const
 {
@@ -988,7 +984,7 @@
 
 bool EffectWindow::isOnDesktop(int d) const
 {
-    const QList<int> ds = desktops();
+    const QVector<int> ds = desktops();
     return ds.isEmpty() || ds.contains(d);
 }