diff --git a/src/types.ml b/src/types.ml
index 5213d091..28a7a7d7 100644
--- a/src/types.ml
+++ b/src/types.ml
@@ -100,6 +100,7 @@ module RsaDenominationKey = struct
   }
 end
 
+(* not implemented *)
 module CSDenominationKey = struct
   (* Clause Schnorr *)
   type t = {