diff --git a/src/api.ml b/src/api.ml
index 18903c50..5c5ac87e 100644
--- a/src/api.ml
+++ b/src/api.ml
@@ -370,3 +370,22 @@ module AuditorSetupMessage = struct
     |> mem "validity_start" Timestamp.jsont ~enc:validity_start
     |> finish
 end
+
+module AuditorTeardownMessage = struct
+  type t = {
+    master_sig: MasterDelAuditorPS.t;
+    (* TODO time
+       something about using monotonic system time here! *)
+    validity_end: Timestamp.t;
+  }
+
+  let jsont =
+    let make master_sig validity_end = { master_sig; validity_end } in
+    let master_sig v = v.master_sig in
+    let validity_end v = v.validity_end in
+    let open Jsont.Object in
+    map ~kind:"AuditorTeardownMessage" make
+    |> mem "master_sig" MasterDelAuditorPS.jsont ~enc:master_sig
+    |> mem "validity_end" Timestamp.jsont ~enc:validity_end
+    |> finish
+end
diff --git a/src/bin_signature.ml b/src/bin_signature.ml
index ebd5d006..af6d0a3b 100644
--- a/src/bin_signature.ml
+++ b/src/bin_signature.ml
@@ -270,6 +270,28 @@ module MasterAddAuditorPS = struct
   include MK (R)
 end
 
+module MasterDelAuditorPS = struct
+  module R = struct
+    (* purpose.purpose = TALER_SIGNATURE_MASTER_DEL_AUDITOR *)
+    type r = {
+      end_date: TimeAbsoluteNBO.t;
+      auditor_pub: AuditorPublicKeyP.t;
+    }
+
+    let bin =
+      let open Bin in
+      Purpose.make_bin Taler_signatures.master_del_auditor @@ fun purpose ->
+      record (fun _purpose end_date auditor_pub -> { end_date; auditor_pub })
+      |+ Purpose.field purpose
+      |+ field TimeAbsoluteNBO.bin (fun t -> t.end_date)
+      |+ field AuditorPublicKeyP.bin (fun t -> t.auditor_pub)
+      |> sealr
+  end
+
+  include R
+  include MK (R)
+end
+
 (* ### BIN IMPL END ### *)
 
 module WithdrawRequestPS = struct
@@ -774,14 +796,6 @@ module CoinPurseRefundConfirmationPS = struct
   }
 end
 
-module MasterDelAuditorPS = struct
-  (* purpose.purpose = TALER_SIGNATURE_MASTER_DEL_AUDITOR *)
-  type t = {
-    end_date: TimeAbsoluteNBO.t;
-    auditor_pub: AuditorPublicKeyP.t;
-  }
-end
-
 module MasterAddWirePS = struct
   (* purpose.purpose = TALER_SIGNATURE_MASTER_ADD_WIRE *)
   type t = {