diff --git a/server_https.hpp b/server_https.hpp
index f6e3b47..4150eb2 100644
--- a/server_https.hpp
+++ b/server_https.hpp
@@ -47,8 +47,10 @@ namespace SimpleWeb {
         // Creating session_id_context from address:port but reversed due to small SSL_MAX_SSL_SESSION_ID_LENGTH
         auto session_id_context = std::to_string(acceptor->local_endpoint().port()) + ':';
         session_id_context.append(config.address.rbegin(), config.address.rend());
-        SSL_CTX_set_session_id_context(context.native_handle(), reinterpret_cast<const unsigned char *>(session_id_context.data()),
-                                       std::min<std::size_t>(session_id_context.size(), SSL_MAX_SSL_SESSION_ID_LENGTH));
+        const auto session_id_length = static_cast<unsigned int>(std::min<std::size_t>(session_id_context.size(), SSL_MAX_SSL_SESSION_ID_LENGTH));
+        SSL_CTX_set_session_id_context(context.native_handle(),
+                                       reinterpret_cast<const unsigned char *>(session_id_context.data()),
+                                       session_id_length);
       }
     }