diff --git a/src/b32.ml b/src/b32.ml
index 29e73239..e22af9b8 100644
--- a/src/b32.ml
+++ b/src/b32.ml
@@ -23,6 +23,4 @@ let decode s =
         | c -> c)
       s
   in
-  match Base32.decode ~alphabet ~off:0 ~len:(String.length s) s with
-  | Error (`Msg e) -> Error e
-  | Ok v -> Ok v
+  Base32.decode ~alphabet ~off:0 ~len:(String.length s) s
diff --git a/src/crypto.ml b/src/crypto.ml
index 7f56a119..29f85403 100644
--- a/src/crypto.ml
+++ b/src/crypto.ml
@@ -10,15 +10,23 @@ module EddsaPublicKey = struct
   type t = pub
 
   let to_octets t = pub_to_octets t
-  let of_octets t = pub_of_octets t |> Result.get_ok
-  let bin = Bin.map (Bin.bytes 32) of_octets to_octets
+  let of_octets t = pub_of_octets t
+
+  let bin =
+    let of_octets o =
+      match of_octets o with
+      | Error e ->
+          let e = Fmt.str "%a" Mirage_crypto_ec.pp_error e in
+          raise (Util.Bin_error e)
+      | Ok v -> v
+    in
+    Bin.map (Bin.bytes 32) of_octets to_octets
 
   let of_b32 s =
     let open Syntax in
     let* octets = B32.decode s in
-    match pub_of_octets octets with
-    | Error e -> Fmt.error "%a" Mirage_crypto_ec.pp_error e
-    | Ok pub -> Ok pub
+    let* pub = of_octets octets in
+    Ok pub
 
   let to_b32 t = B32.encode (to_octets t)
   let jsont = Jsont.of_of_string ~kind:"EddsaPublicKey" of_b32 ~enc:to_b32
diff --git a/src/util.ml b/src/util.ml
index 31be5ef4..731f8244 100644
--- a/src/util.ml
+++ b/src/util.ml
@@ -1,3 +1,5 @@
+exception Bin_error of string
+
 (* TODO bin
    - no [Bin.of_string] ? *)
 let bin_of_string bin s =
@@ -52,7 +54,7 @@ module Bin_rsa = struct
       Bytes.unsafe_to_string b
 
     let check = function
-      | false -> Error "rsa of_octets error, invalid data"
+      | false -> Error (`Msg "rsa of_octets error, invalid data")
       | true -> Ok ()
 
     let z_array_of_octets ~nb s =
@@ -88,7 +90,7 @@ module Bin_rsa = struct
     let* arr = z_array_of_octets ~nb:2 s in
     match arr with
     | [| n; e |] ->
-        let+ pub = Mirage_crypto_pk.Rsa.pub ~n ~e |> unwrap_err_msg in
+        let+ pub = Mirage_crypto_pk.Rsa.pub ~n ~e in
         pub
     | _ -> assert false
 
@@ -100,9 +102,7 @@ module Bin_rsa = struct
     let* arr = z_array_of_octets ~nb:8 s in
     match arr with
     | [| e; d; n; p; q; dp; dq; q' |] ->
-        let+ priv =
-          Mirage_crypto_pk.Rsa.priv ~e ~d ~n ~p ~q ~dp ~dq ~q' |> unwrap_err_msg
-        in
+        let+ priv = Mirage_crypto_pk.Rsa.priv ~e ~d ~n ~p ~q ~dp ~dq ~q' in
         priv
     | _ -> assert false
 end