diff --git a/coding/value_opt_string.hpp b/coding/value_opt_string.hpp
index 1b197cd1ee..3aff7f79b3 100644
--- a/coding/value_opt_string.hpp
+++ b/coding/value_opt_string.hpp
@@ -72,3 +72,8 @@ public:
     }
   }
 };
+
+string DebugPrint(StringNumericOptimal const & s)
+{
+  return s.Get();
+}