diff --git a/server/plugin/plg_backend_s3/index.go b/server/plugin/plg_backend_s3/index.go
index f0039900..d1795c75 100644
--- a/server/plugin/plg_backend_s3/index.go
+++ b/server/plugin/plg_backend_s3/index.go
@@ -213,7 +213,7 @@ func (this S3Backend) Ls(path string) (files []os.FileInfo, err error) {
 				}
 				size := 0
 				if object.Size != nil {
-					size = *object.Size
+					size = int(*object.Size)
 				}
 				files = append(files, &File{
 					FName: filepath.Base(*object.Key),