diff --git a/gdk/broadway/gdkscreen-broadway.c b/gdk/broadway/gdkscreen-broadway.c
index f970be91e1..285aa988eb 100644
--- a/gdk/broadway/gdkscreen-broadway.c
+++ b/gdk/broadway/gdkscreen-broadway.c
@@ -150,8 +150,6 @@ static gint
 gdk_broadway_screen_get_monitor_width_mm (GdkScreen *screen,
 					  gint       monitor_num)
 {
-  g_return_val_if_fail (monitor_num == 0, -1);
-
   return gdk_screen_get_width_mm (screen);
 }
 
@@ -159,8 +157,6 @@ static gint
 gdk_broadway_screen_get_monitor_height_mm (GdkScreen *screen,
 					   gint       monitor_num)
 {
-  g_return_val_if_fail (monitor_num == 0, -1);
-
   return gdk_screen_get_height_mm (screen);
 }
 
@@ -168,8 +164,6 @@ static gchar *
 gdk_broadway_screen_get_monitor_plug_name (GdkScreen *screen,
 					   gint       monitor_num)
 {
-  g_return_val_if_fail (monitor_num == 0, NULL);
-
   return g_strdup ("browser");
 }
 
@@ -180,8 +174,6 @@ gdk_broadway_screen_get_monitor_geometry (GdkScreen    *screen,
 {
   GdkBroadwayScreen *broadway_screen = GDK_BROADWAY_SCREEN (screen);
 
-  g_return_if_fail (monitor_num == 0);
-
   if (dest)
     {
       dest->x = 0;
diff --git a/gdk/gdkscreen.c b/gdk/gdkscreen.c
index 0ed04b14c1..33e2ce983d 100644
--- a/gdk/gdkscreen.c
+++ b/gdk/gdkscreen.c
@@ -725,6 +725,7 @@ gdk_screen_get_monitor_width_mm	(GdkScreen *screen,
 {
   g_return_val_if_fail (GDK_IS_SCREEN (screen), -1);
   g_return_val_if_fail (monitor_num >= 0, -1);
+  g_return_val_if_fail (monitor_num < gdk_screen_get_n_monitors (screen), -1);
 
   return GDK_SCREEN_GET_CLASS (screen)->get_monitor_width_mm (screen, monitor_num);
 }
@@ -746,6 +747,7 @@ gdk_screen_get_monitor_height_mm (GdkScreen *screen,
 {
   g_return_val_if_fail (GDK_IS_SCREEN (screen), -1);
   g_return_val_if_fail (monitor_num >= 0, -1);
+  g_return_val_if_fail (monitor_num < gdk_screen_get_n_monitors (screen), -1);
 
   return GDK_SCREEN_GET_CLASS (screen)->get_monitor_height_mm (screen, monitor_num);
 }
@@ -770,6 +772,7 @@ gdk_screen_get_monitor_plug_name (GdkScreen *screen,
 {
   g_return_val_if_fail (GDK_IS_SCREEN (screen), NULL);
   g_return_val_if_fail (monitor_num >= 0, NULL);
+  g_return_val_if_fail (monitor_num < gdk_screen_get_n_monitors (screen), NULL);
 
   return GDK_SCREEN_GET_CLASS (screen)->get_monitor_plug_name (screen, monitor_num);
 }
@@ -799,6 +802,7 @@ gdk_screen_get_monitor_geometry (GdkScreen    *screen,
 {
   g_return_if_fail (GDK_IS_SCREEN (screen));
   g_return_if_fail (monitor_num >= 0);
+  g_return_if_fail (monitor_num < gdk_screen_get_n_monitors (screen));
 
   GDK_SCREEN_GET_CLASS(screen)->get_monitor_geometry (screen, monitor_num, dest);
 }
@@ -829,6 +833,7 @@ gdk_screen_get_monitor_workarea (GdkScreen    *screen,
 {
   g_return_if_fail (GDK_IS_SCREEN (screen));
   g_return_if_fail (monitor_num >= 0);
+  g_return_if_fail (monitor_num < gdk_screen_get_n_monitors (screen));
 
   GDK_SCREEN_GET_CLASS (screen)->get_monitor_workarea (screen, monitor_num, dest);
 }
diff --git a/gdk/wayland/gdkscreen-wayland.c b/gdk/wayland/gdkscreen-wayland.c
index 47f70ef41e..ff03c5eaa1 100644
--- a/gdk/wayland/gdkscreen-wayland.c
+++ b/gdk/wayland/gdkscreen-wayland.c
@@ -220,8 +220,6 @@ gdk_wayland_screen_get_monitor_width_mm	(GdkScreen *screen,
 {
   GdkScreenWayland *screen_wayland = GDK_SCREEN_WAYLAND (screen);
 
-  g_return_val_if_fail (monitor_num < screen_wayland->n_monitors, -1);
-
   return screen_wayland->monitors[monitor_num].width_mm;
 }
 
@@ -231,8 +229,6 @@ gdk_wayland_screen_get_monitor_height_mm (GdkScreen *screen,
 {
   GdkScreenWayland *screen_wayland = GDK_SCREEN_WAYLAND (screen);
 
-  g_return_val_if_fail (monitor_num < screen_wayland->n_monitors, -1);
-
   return screen_wayland->monitors[monitor_num].height_mm;
 }
 
@@ -242,8 +238,6 @@ gdk_wayland_screen_get_monitor_plug_name (GdkScreen *screen,
 {
   GdkScreenWayland *screen_wayland = GDK_SCREEN_WAYLAND (screen);
 
-  g_return_val_if_fail (monitor_num < screen_wayland->n_monitors, NULL);
-
   return g_strdup (screen_wayland->monitors[monitor_num].output_name);
 }
 
@@ -254,8 +248,6 @@ gdk_wayland_screen_get_monitor_geometry (GdkScreen    *screen,
 {
   GdkScreenWayland *screen_wayland = GDK_SCREEN_WAYLAND (screen);
 
-  g_return_if_fail (monitor_num < screen_wayland->n_monitors);
-
   if (dest)
     *dest = screen_wayland->monitors[monitor_num].geometry;
 }
diff --git a/gdk/x11/gdkscreen-x11.c b/gdk/x11/gdkscreen-x11.c
index 650336b33e..6a7463638b 100644
--- a/gdk/x11/gdkscreen-x11.c
+++ b/gdk/x11/gdkscreen-x11.c
@@ -213,8 +213,6 @@ gdk_x11_screen_get_monitor_width_mm (GdkScreen *screen,
 {
   GdkX11Screen *x11_screen = GDK_X11_SCREEN (screen);
 
-  g_return_val_if_fail (monitor_num < x11_screen->n_monitors, -1);
-
   return x11_screen->monitors[monitor_num].width_mm;
 }
 
@@ -224,8 +222,6 @@ gdk_x11_screen_get_monitor_height_mm (GdkScreen *screen,
 {
   GdkX11Screen *x11_screen = GDK_X11_SCREEN (screen);
 
-  g_return_val_if_fail (monitor_num < x11_screen->n_monitors, -1);
-
   return x11_screen->monitors[monitor_num].height_mm;
 }
 
@@ -235,8 +231,6 @@ gdk_x11_screen_get_monitor_plug_name (GdkScreen *screen,
 {
   GdkX11Screen *x11_screen = GDK_X11_SCREEN (screen);
 
-  g_return_val_if_fail (monitor_num < x11_screen->n_monitors, NULL);
-
   return g_strdup (x11_screen->monitors[monitor_num].output_name);
 }
 
@@ -273,8 +267,6 @@ gdk_x11_screen_get_monitor_geometry (GdkScreen    *screen,
 {
   GdkX11Screen *x11_screen = GDK_X11_SCREEN (screen);
 
-  g_return_if_fail (monitor_num < x11_screen->n_monitors);
-
   if (dest)
     *dest = x11_screen->monitors[monitor_num].geometry;
 }