diff --git a/ulog_cpp/messages.hpp b/ulog_cpp/messages.hpp
index aa471e8..2f5769a 100644
--- a/ulog_cpp/messages.hpp
+++ b/ulog_cpp/messages.hpp
@@ -586,7 +586,7 @@ class MessageFormat {
   /**
    * @return the list of fields, in-order
    */
-  std::vector<std::shared_ptr<Field>> fields() const { return _fields_ordered; }
+  const std::vector<std::shared_ptr<Field>>& fields() const { return _fields_ordered; }
 
   /**
    * @return the list of field names, in-order