diff --git a/grub-core/gfxmenu/theme_loader.c b/grub-core/gfxmenu/theme_loader.c
index 1a6ed1d25..02978392c 100644
--- a/grub-core/gfxmenu/theme_loader.c
+++ b/grub-core/gfxmenu/theme_loader.c
@@ -255,7 +255,7 @@ theme_set_string (grub_gfxmenu_view_t view,
     {
       unsigned int tmp;
       int err = theme_get_unsigned_int_from_proportional (value,
-                                                          view->screen.width,
+                                                          view->screen.height,
                                                           &tmp);
       if (err != GRUB_ERR_NONE)
         return err;
@@ -275,7 +275,7 @@ theme_set_string (grub_gfxmenu_view_t view,
     {
       unsigned int tmp;
       int err = theme_get_unsigned_int_from_proportional (value,
-                                                          view->screen.width,
+                                                          view->screen.height,
                                                           &tmp);
       if (err != GRUB_ERR_NONE)
         return err;