diff --git a/internal/ceres/map_util.h b/internal/ceres/map_util.h
index 61c531f..f55aee3 100644
--- a/internal/ceres/map_util.h
+++ b/internal/ceres/map_util.h
@@ -67,7 +67,7 @@
 // If the key is present in the map then the value associated with that
 // key is returned, otherwise the value passed as a default is returned.
 template <class Collection>
-const typename Collection::value_type::second_type&
+const typename Collection::value_type::second_type
 FindWithDefault(const Collection& collection,
                 const typename Collection::value_type::first_type& key,
                 const typename Collection::value_type::second_type& value) {