diff --git a/vfs/vfs.go b/vfs/vfs.go
index 3813a0817..e436fb3ff 100644
--- a/vfs/vfs.go
+++ b/vfs/vfs.go
@@ -48,6 +48,8 @@ var DefaultOpt = Options{
 	CacheMode:         CacheModeOff,
 	CacheMaxAge:       3600 * time.Second,
 	CachePollInterval: 60 * time.Second,
+	ChunkSize:         128 * fs.MebiByte,
+	ChunkSizeLimit:    -1,
 }
 
 // Node represents either a directory (*Dir) or a file (*File)
diff --git a/vfs/vfsflags/vfsflags.go b/vfs/vfsflags/vfsflags.go
index 6ae07c38b..47abf8eab 100644
--- a/vfs/vfsflags/vfsflags.go
+++ b/vfs/vfsflags/vfsflags.go
@@ -24,6 +24,6 @@ func AddFlags(flagSet *pflag.FlagSet) {
 	flags.DurationVarP(flagSet, &Opt.CachePollInterval, "vfs-cache-poll-interval", "", Opt.CachePollInterval, "Interval to poll the cache for stale objects.")
 	flags.DurationVarP(flagSet, &Opt.CacheMaxAge, "vfs-cache-max-age", "", Opt.CacheMaxAge, "Max age of objects in the cache.")
 	flags.FVarP(flagSet, &Opt.ChunkSize, "vfs-read-chunk-size", "", "Read the source objects in chunks.")
-	flags.FVarP(flagSet, &Opt.ChunkSizeLimit, "vfs-read-chunk-size-limit", "", "If greater than --vfs-read-chunk-size, double the chunk size after each chunk read, until the limit is reached. -1 is unlimited.")
+	flags.FVarP(flagSet, &Opt.ChunkSizeLimit, "vfs-read-chunk-size-limit", "", "If greater than --vfs-read-chunk-size, double the chunk size after each chunk read, until the limit is reached. 'off' is unlimited.")
 	platformFlags(flagSet)
 }