diff --git a/src/denomination.ml b/src/denomination.ml
index 65afdcc2..32abbfd3 100644
--- a/src/denomination.ml
+++ b/src/denomination.ml
@@ -15,7 +15,7 @@ type t = {
   age_mask: int;
   h_pub: Bin_type.DenominationHash.t;
   sign: string -> RsaSignature.t;
-  master_sig: EddsaSignature.t option;
+  master_sig: EddsaSignature.t;
 }
 
 let make
@@ -50,7 +50,7 @@ let make
   let pub = pub_of_priv priv in
   let h_pub = Bin_type.DenominationHash.hash (RsaPublicKey.to_octets pub) in
   let sign = RsaSignature.sign ~key:priv in
-  let master_sig = None in
+  let master_sig = EddsaSignature.of_octets (String.make 64 'x') in
   {
     pub;
     section_name;
diff --git a/src/pg.ml b/src/pg.ml
index 769cfe46..160ea1d3 100644
--- a/src/pg.ml
+++ b/src/pg.ml
@@ -97,12 +97,9 @@ let activate_signing_key =
   in
   fun (module Conn : CONN) exchange_signkey ->
     let Signkey.
-          { pub; stamp_start; stamp_expire; stamp_end; master_sig= _; sign= _ }
-        =
+          { pub; stamp_start; stamp_expire; stamp_end; master_sig; sign= _ } =
       exchange_signkey
     in
-    (*let master_sig = master_sig |> Option.get in*)
-    let master_sig = EddsaSignature.of_octets (String.make 64 'x') in
     Conn.exec insert_signkey
       (pub, stamp_start, stamp_expire, stamp_end, master_sig)
 
@@ -151,7 +148,6 @@ let add_denomination_key =
           } =
       denom
     in
-    let master_sig = master_sig |> Option.get in
     Conn.exec denomination_insert
       ( h_pub,
         pub,
diff --git a/src/signkey.ml b/src/signkey.ml
index 01095f00..a74b0173 100644
--- a/src/signkey.ml
+++ b/src/signkey.ml
@@ -1,5 +1,6 @@
 open Crypto
 
+(* TODO master_sig: use option? *)
 type t = {
   pub: EddsaPublicKey.t;
   stamp_start: Ptime.t;
@@ -7,7 +8,7 @@ type t = {
   stamp_end: Ptime.t;
   sign: string -> EddsaSignature.t;
   (* signature of this key by offline master key *)
-  master_sig: EddsaSignature.t option;
+  master_sig: EddsaSignature.t;
 }
 
 let generate () =
@@ -24,5 +25,6 @@ let generate () =
   let stamp_end = stamp_expire in
   let priv, pub = Mirage_crypto_ec.Ed25519.generate () in
   let sign s = EddsaSignature.sign ~key:priv s in
-  let master_sig = None in
+  (* dummy master_sig *)
+  let master_sig = EddsaSignature.of_octets (String.make 64 'x') in
   { pub; stamp_start; stamp_expire; stamp_end; master_sig; sign }