diff --git a/include/date/tz_private.h b/include/date/tz_private.h
index ae04f29..1aaad8e 100644
--- a/include/date/tz_private.h
+++ b/include/date/tz_private.h
@@ -291,6 +291,7 @@ struct transition
     {
         using namespace date;
         using namespace std::chrono;
+        using date::operator<<;
         os << t.timepoint << "Z ";
         if (t.info->offset >= seconds{0})
             os << '+';