diff --git a/gdk/x11/gdkdisplay-x11.c b/gdk/x11/gdkdisplay-x11.c
index 1386acbb49..15dd1a5a5f 100644
--- a/gdk/x11/gdkdisplay-x11.c
+++ b/gdk/x11/gdkdisplay-x11.c
@@ -2951,7 +2951,7 @@ gdk_x11_display_get_monitor (GdkDisplay *display,
 {
   GdkX11Display *x11_display = GDK_X11_DISPLAY (display);
 
-  if (0 <= monitor_num || monitor_num < x11_display->monitors->len)
+  if (0 <= monitor_num && monitor_num < x11_display->monitors->len)
     return (GdkMonitor *)x11_display->monitors->pdata[monitor_num];
 
   return NULL;