diff --git a/src/shan.cpp b/src/shan.cpp
index 69e67c5..4b4654f 100644
--- a/src/shan.cpp
+++ b/src/shan.cpp
@@ -5,7 +5,7 @@
 namespace cmajiang {
 
 Shan::Shan(const Rule& rule, std::mt19937_64& mt)
-    : _rule(rule), _weikaigang(false), _closed(false), _engine(&mt) {
+    : _rule(rule), _weikaigang(false), _closed(false) {
   for (const auto s : {'m', 'p', 's', 'z'}) {
     for (int n = 1; n <= (s == 'z' ? 7 : 9); n++) {
       for (int i = 0; i < 4; i++) {
@@ -16,7 +16,7 @@ Shan::Shan(const Rule& rule, std::mt19937_64& mt)
       }
     }
   }
-  std::shuffle(_pai.begin(), _pai.end(), *_engine);
+  std::shuffle(_pai.begin(), _pai.end(), mt);
 
   _baopai.emplace_back(_pai[4]);
   // 裏ドラあり
diff --git a/src/shan.h b/src/shan.h
index 6284d24..80965eb 100644
--- a/src/shan.h
+++ b/src/shan.h
@@ -70,7 +70,6 @@ class Shan {
   std::vector<std::string> _libaopai;  // 里宝牌(裏ドラ)
   bool _weikaigang;                    // 未开杠(未開槓)
   bool _closed;
-  std::mt19937_64* _engine;
 };
 
 inline std::ostream& operator<<(std::ostream& os, const Shan& shan) {