diff --git a/src/config.hpp b/src/config.hpp
index 8409eb9d..dba89c6b 100644
--- a/src/config.hpp
+++ b/src/config.hpp
@@ -139,7 +139,7 @@ public:
   NFSOpenHack    nfsopenhack;
   ConfigBOOL     nullrw;
   ConfigBOOL     parallel_direct_writes;
-  ConfigBool     passthrough;
+  ConfigBOOL     passthrough;
   ConfigGetPid   pid;
   ConfigBOOL     posix_acl;
   ConfigUINT64   readahead;