diff --git a/tests/src/unit-convenience.cpp b/tests/src/unit-convenience.cpp
index 839f1c86e..7476c75cb 100644
--- a/tests/src/unit-convenience.cpp
+++ b/tests/src/unit-convenience.cpp
@@ -98,7 +98,8 @@ void check_escaped(const char* original, const char* escaped = "", bool ensure_a
 void check_escaped(const char* original, const char* escaped, const bool ensure_ascii)
 {
     std::stringstream ss;
-    json::serializer s(nlohmann::detail::output_adapter<char>(ss), ' ');
+    nlohmann::detail::output_stream_adapter<char> adapter(ss);
+    json::serializer s(&adapter, ' ');
     s.dump_escaped(original, ensure_ascii);
     s.flush(); // dump_escaped writes into the serializer's internal buffer
     CHECK(ss.str() == escaped);