diff --git a/src/config_passthrough.cpp b/src/config_passthrough.cpp
index d656d81a..b2bf6787 100644
--- a/src/config_passthrough.cpp
+++ b/src/config_passthrough.cpp
@@ -24,7 +24,7 @@ template<>
 std::string
 Passthrough::to_string() const
 {
-  return BE_Passthrough::_from_integral((int)_data).to_string();
+  return BE_Passthrough::_from_integral((int)_data)._to_string();
 }
 
 template<>