diff --git a/grub-core/gfxmenu/gui_label.c b/grub-core/gfxmenu/gui_label.c
index a4c817891..1c190542a 100644
--- a/grub-core/gfxmenu/gui_label.c
+++ b/grub-core/gfxmenu/gui_label.c
@@ -193,6 +193,10 @@ label_set_property (void *vself, const char *name, const char *value)
 	   else if (grub_strcmp (value, "@KEYMAP_SHORT@") == 0)
 	    value = _("enter: boot, `e': options, `c': cmd-line");
 	   /* FIXME: Add more templates here if needed.  */
+
+	  if (grub_printf_fmt_check(value, "%d") != GRUB_ERR_NONE)
+	    value = ""; /* Unsupported format. */
+
 	  self->template = grub_strdup (value);
 	  self->text = grub_xasprintf (value, self->value);
 	}
diff --git a/grub-core/gfxmenu/gui_progress_bar.c b/grub-core/gfxmenu/gui_progress_bar.c
index b128f0866..ace85a125 100644
--- a/grub-core/gfxmenu/gui_progress_bar.c
+++ b/grub-core/gfxmenu/gui_progress_bar.c
@@ -348,6 +348,9 @@ progress_bar_set_property (void *vself, const char *name, const char *value)
 	   Please use the shortest form available in you language.  */
 	value = _("%ds");
 
+      if (grub_printf_fmt_check(value, "%d") != GRUB_ERR_NONE)
+	value = ""; /* Unsupported format. */
+
       self->template = grub_strdup (value);
     }
   else if (grub_strcmp (name, "font") == 0)