diff --git a/private/taskq.rkt b/private/taskq.rkt
index 883e4bb..cf208b0 100644
--- a/private/taskq.rkt
+++ b/private/taskq.rkt
@@ -90,7 +90,8 @@
     (for ([w (in-set dequeue-waiters)])
       (thread-send w #f #f))
     (for ([(k v) (in-hash task-waiters)])
-      (thread-send v (error "queue shutdown") #f)))
+      (for ([w (in-set v)])
+        (thread-send w (error "queue shutdown") #f))))
 
   ;; attempts to dequeue the next work
   ;; if there is work, set it to executing and invoke and remove one of the workers