diff --git a/params.go b/params.go
index f523fa0..eaab2d0 100644
--- a/params.go
+++ b/params.go
@@ -282,6 +282,8 @@ func (params Params) encodeMultipartForm(writer io.Writer) (mime string, err err
 				return
 			}
 
+			defer file.Close() 
+
 			_, err = io.Copy(dst, file)
 
 			if err != nil {