diff --git a/xls/cfb/interface.go b/xls/cfb/interface.go
index ec5a6a9..26bd0af 100644
--- a/xls/cfb/interface.go
+++ b/xls/cfb/interface.go
@@ -13,6 +13,7 @@ func Open(filename string) (*Document, error) {
 	if err != nil {
 		return nil, err
 	}
+	defer f.Close()
 	err = d.load(f)
 	if err != nil {
 		return nil, err