diff --git a/src/database/row.hpp b/src/database/row.hpp
index e7a58c4..a8e8579 100644
--- a/src/database/row.hpp
+++ b/src/database/row.hpp
@@ -45,7 +45,7 @@ struct Row
     {}
 
     template <typename Type>
-    auto& col()
+    typename Type::real_type& col()
     {
       auto&& col = std::get<Type>(this->columns);
       return col.value;