diff --git a/pkg/fs/preload.go b/pkg/fs/preload.go
index 7030c41..396cf8b 100644
--- a/pkg/fs/preload.go
+++ b/pkg/fs/preload.go
@@ -84,7 +84,9 @@ func (r *Rate) SetReader(reader io.Reader) {
 
 func (r *Rate) Read(b []byte) (n int, err error) {
 	n, err = r.r.Read(b)
-	atomic.AddInt64(&r.num, int64(n))
+	if n > 0 {
+		atomic.AddInt64(&r.num, int64(n))
+	}
 	return
 }