diff --git a/src/secmod_denom.ml b/src/secmod_denom.ml
index 1e4f539c..28bc7f25 100644
--- a/src/secmod_denom.ml
+++ b/src/secmod_denom.ml
@@ -4,7 +4,8 @@ type rsa = {
   sign:
     (* TODO sig type
        should be
-       string -> RsaSignature.t *)
+       string -> RsaSignature.t
+       + b32 *)
     string ->
     string;
 }
diff --git a/src/secmod_keys.ml b/src/secmod_keys.ml
index 809e65c4..df3e280c 100644
--- a/src/secmod_keys.ml
+++ b/src/secmod_keys.ml
@@ -3,7 +3,8 @@ type t = {
   sign:
     (* TODO sig type
        should be
-       string -> EddsaSignature.t *)
+       string -> EddsaSignature.t
+       + b32 *)
     string ->
     string;
 }