diff --git a/ssh-transport.rkt b/ssh-transport.rkt
index d507033..dae2c05 100644
--- a/ssh-transport.rkt
+++ b/ssh-transport.rkt
@@ -116,7 +116,8 @@
 			      packet
 			      write-packet!
 			      (lambda (new-seed) (loop new-seed
-						       (+ sequence-number 1)
+						       (bitwise-and (+ sequence-number 1)
+								    #xffffffff)
 						       cipher
 						       check-mac!))
 			      (lambda args