diff --git a/collects/mzlib/async-channel.ss b/collects/mzlib/async-channel.ss
index 30f8170..6ae4bff 100644
--- a/collects/mzlib/async-channel.ss
+++ b/collects/mzlib/async-channel.ss
@@ -76,7 +76,7 @@
 		    [(zero? size)
 		     ;; The queue is currently empty:
 		     (sync enqueue tell-empty)]
-		    [(or (not limit) ((sub1 size) . < . limit))
+		    [(or (not limit) (size . < . limit))
 		     (sync enqueue (mk-dequeue))]
 		    [else
 		     (sync (mk-dequeue) tell-full)])