diff --git a/src/virt-viewer-display-spice.c b/src/virt-viewer-display-spice.c
index 22fde46..c4681eb 100644
--- a/src/virt-viewer-display-spice.c
+++ b/src/virt-viewer-display-spice.c
@@ -200,7 +200,8 @@ virt_viewer_display_spice_size_allocate(VirtViewerDisplaySpice *self,
         GdkRectangle monitor;
         GdkScreen *screen = gtk_widget_get_screen(GTK_WIDGET(self));
         GdkWindow *window = gtk_widget_get_root_window(GTK_WIDGET(self));
-        int n = gdk_screen_get_monitor_at_window(screen, window);
+        int n = gdk_screen_get_monitor_at_window(screen,
+                                     gtk_widget_get_window(GTK_WIDGET(self)));
         gdk_screen_get_monitor_geometry(screen, n, &monitor);
         dw = monitor.width;
         dh = monitor.height;