diff --git a/src/Pinyin.php b/src/Pinyin.php
index 2fbfe656..1fe4ebee 100644
--- a/src/Pinyin.php
+++ b/src/Pinyin.php
@@ -317,7 +317,7 @@ protected function formatTone($pinyin, $option = \PINYIN_NO_TONE)
     {
         $replacements = [
             // mb_chr(593) => 'ɑ' 轻声中除了 `ɑ` 和 `ü` 以外，其它和字母一样
-            'ɑ' => ['a', 5], 'ü' => ['v', 5],
+            'ɑ' => ['a', 5], 'ü' => ['yu', 5],
             'üē' => ['ue', 1], 'üé' => ['ue', 2], 'üě' => ['ue', 3], 'üè' => ['ue', 4],
             'ā' => ['a', 1], 'ē' => ['e', 1], 'ī' => ['i', 1], 'ō' => ['o', 1], 'ū' => ['u', 1], 'ǖ' => ['yu', 1],
             'á' => ['a', 2], 'é' => ['e', 2], 'í' => ['i', 2], 'ó' => ['o', 2], 'ú' => ['u', 2], 'ǘ' => ['yu', 2],