diff --git a/common/spl/spl_blk_fs.c b/common/spl/spl_blk_fs.c
index d4161fa..16ecece 100644
--- a/common/spl/spl_blk_fs.c
+++ b/common/spl/spl_blk_fs.c
@@ -66,7 +66,7 @@
 	}
 
 	dev.ifname = blk_get_uclass_name(uclass_id);
-	snprintf(dev.dev_part_str, sizeof(dev.dev_part_str) - 1, "%d:%d",
+	snprintf(dev.dev_part_str, sizeof(dev.dev_part_str) - 1, "%x:%x",
 		 devnum, partnum);
 	ret = fs_set_blk_dev(dev.ifname, dev.dev_part_str, FS_TYPE_ANY);
 	if (ret) {