diff --git a/syndicate-ssh/crypto.rkt b/syndicate-ssh/crypto.rkt
index c8f5a5d..328e2ac 100644
--- a/syndicate-ssh/crypto.rkt
+++ b/syndicate-ssh/crypto.rkt
@@ -2,8 +2,15 @@
 ;;; SPDX-License-Identifier: LGPL-3.0-or-later
 ;;; SPDX-FileCopyrightText: Copyright © 2011-2021 Tony Garnock-Jones <tonyg@leastfixedpoint.com>
 
-(provide (all-from-out crypto))
+(provide (all-from-out crypto)
+         (all-defined-out))
 
 (require crypto)
 (require crypto/all)
 (use-all-factories!)
+
+(define (sha1 bs)
+  (digest 'sha1 bs))
+
+(define (sha256 bs)
+  (digest 'sha256 bs))
diff --git a/syndicate-ssh/ssh-session.rkt b/syndicate-ssh/ssh-session.rkt
index c8f8185..a0448a3 100644
--- a/syndicate-ssh/ssh-session.rkt
+++ b/syndicate-ssh/ssh-session.rkt
@@ -4,7 +4,6 @@
 
 (require bitsyntax)
 (require syndicate/drivers/timer)
-(require (only-in file/sha1 sha1))
 
 (require "crypto.rkt")
 (require "oakley-groups.rkt")