diff --git a/tests/daemon/face/websocket-channel-fixture.hpp b/tests/daemon/face/websocket-channel-fixture.hpp
index 3072992..62c717b 100644
--- a/tests/daemon/face/websocket-channel-fixture.hpp
+++ b/tests/daemon/face/websocket-channel-fixture.hpp
@@ -39,7 +39,7 @@
 protected:
   shared_ptr<WebSocketChannel>
   makeChannel(const boost::asio::ip::address& addr, uint16_t port = 0,
-              optional<size_t> mtu = nullopt) final
+              std::optional<size_t> mtu = std::nullopt) final
   {
     if (port == 0)
       port = getNextPort();