diff --git a/src/config_passthrough.cpp b/src/config_passthrough.cpp
index 17cc1e29..d7a03f52 100644
--- a/src/config_passthrough.cpp
+++ b/src/config_passthrough.cpp
@@ -31,7 +31,9 @@ template<>
 int
 Passthrough::from_string(const std::string &s_)
 {
-  auto x = PassthroughEnum::_from_string_nothrow(s_.c_str());
+  better_enums::optional<PassthroughEnum> e;
+
+  e = PassthroughEnum::_from_string_nothrow(s_.c_str());
 
   if(!x)
     return -EINVAL;