diff --git a/include/boost/asio/detail/scoped_lock.hpp b/include/boost/asio/detail/scoped_lock.hpp
index 848864e9..d955e2b0 100644
--- a/include/boost/asio/detail/scoped_lock.hpp
+++ b/include/boost/asio/detail/scoped_lock.hpp
@@ -69,8 +69,8 @@ class scoped_lock
   {
     if (locked_)
     {
-      mutex_.unlock();
       locked_ = false;
+      mutex_.unlock();
     }
   }