diff --git a/src/config.hpp b/src/config.hpp
index db98c183..e668a56e 100644
--- a/src/config.hpp
+++ b/src/config.hpp
@@ -85,7 +85,7 @@ public:
   Config& operator=(const Config&);
 
 public:
-  TFSRef<>       foo;
+  TFSRef<bool>   foo;
   ConfigBOOL     allow_idmap;
   ConfigBOOL     async_read;
   ConfigBOOL     auto_cache;