diff -Naru grub-extras-master.orig/lua/grub_lib.c grub-extras-master/lua/grub_lib.c
--- grub-extras-master.orig/lua/grub_lib.c	2013-12-25 01:06:47.000000000 +0700
+++ grub-extras-master/lua/grub_lib.c	2015-02-27 18:15:33.002264978 +0700
@@ -183,7 +183,27 @@
 		}
 	    }
 
-	  lua_call (state, 3, 1);
+	  if (! fs->label)
+	    lua_pushnil (state);
+	  else
+	    {
+	      int err;
+	      char *label;
+
+	      err = fs->label (dev, &label);
+	      if (err)
+		{
+		  grub_errno = 0;
+		  lua_pushnil (state);
+		}
+	      else
+		{
+		  lua_pushstring (state, label);
+		  grub_free (label);
+		}
+	    }
+
+	  lua_call (state, 4, 1);
 	  result = lua_tointeger (state, -1);
 	  lua_pop (state, 1);
 	}