diff --git a/grub-core/net/drivers/ieee1275/ofnet.c b/grub-core/net/drivers/ieee1275/ofnet.c
index 8c8398948..78f03df8e 100644
--- a/grub-core/net/drivers/ieee1275/ofnet.c
+++ b/grub-core/net/drivers/ieee1275/ofnet.c
@@ -220,8 +220,7 @@ grub_ieee1275_parse_bootpath (const char *devpath, char *bootpath,
                                  flags);
       inter->vlantag = vlantag;
       grub_net_add_ipv4_local (inter,
-                          __builtin_ctz (~grub_le_to_cpu32 (subnet_mask.ipv4)));
-
+                          __builtin_clz (~grub_be_to_cpu32 (subnet_mask.ipv4)));
     }
 
   if (gateway_addr.ipv4 != 0)