diff --git a/src/http_info.ml b/src/http_info.ml
index 96d39db7..90e10dc2 100644
--- a/src/http_info.ml
+++ b/src/http_info.ml
@@ -103,15 +103,17 @@ let mk_keys ~db_conn (module Keys : Keys.S) ~last_issue_date =
     |> List.map Api.SignKey.of_signkey
   in
 
-  let exchange_pub =
-    (* the eddsa pub key used to sign exchange_sig *)
+  (* the eddsa pub key used to sign exchange_sig *)
+  let* exchange_pub =
     match signkeys with
-    | [] -> Fmt.failwith "exchange has no active signkey"
-    | sk :: _ -> sk.SignKey.key
+    | [] -> Fmt.error "exchange has no active signkey"
+    | sk :: _ -> Ok sk.SignKey.key
   in
+
+  (* TODO *)
+  (* Compact eddsa signature over the contatentation of all of the master_sigs
+     (in reverse chronological order by group) in the arrays under "denominations" *)
   let exchange_sig =
-    (* Compact eddsa signature over the contatentation of all of the master_sigs
-       (in reverse chronological order by group) in the arrays under "denominations" *)
     let hc =
       denom_l
       |> List.map (fun dn -> dn.Denomination.master_sig)
@@ -184,9 +186,7 @@ let keys req server _env =
       | [] -> Ok None
       | s :: _ -> (
           match Int64.of_string_opt s with
-          | None ->
-              Error
-                "invalid `?last_issue_date` query param, int_of_string failure"
+          | None -> Error "invalid `?last_issue_date` query param, not an int"
           | Some n -> Ok (Some (Timestamp.of_s n)))
     in
     let* v = mk_keys ~db_conn keys ~last_issue_date in