diff --git a/include/boost/asio/ssl/detail/impl/engine.ipp b/include/boost/asio/ssl/detail/impl/engine.ipp
index 57933108..71a91f9e 100644
--- a/include/boost/asio/ssl/detail/impl/engine.ipp
+++ b/include/boost/asio/ssl/detail/impl/engine.ipp
@@ -101,6 +101,12 @@ engine& engine::operator=(engine&& other) noexcept
 {
   if (this != &other)
   {
+    if (ssl_ && SSL_get_app_data(ssl_))
+    {
+      delete static_cast<verify_callback_base*>(SSL_get_app_data(ssl_));
+      SSL_set_app_data(ssl_, 0);
+    }
+
     if (ext_bio_)
       ::BIO_free(ext_bio_);