diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 0570391eaa16..23790c7b2289 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -1919,7 +1919,7 @@ static int nfs_parse_devname(const char *dev_name,
 		/* kill possible hostname list: not supported */
 		comma = strchr(dev_name, ',');
 		if (comma != NULL && comma < end)
-			*comma = 0;
+			len = comma - dev_name;
 	}
 
 	if (len > maxnamlen)