diff --git a/syndicate/dataspace.rkt b/syndicate/dataspace.rkt
index 6aa0087..3f99fba 100644
--- a/syndicate/dataspace.rkt
+++ b/syndicate/dataspace.rkt
@@ -413,7 +413,8 @@
 ;; Abruptly terminates an entire actor, without running stop-scripts etc.
 (define (terminate-actor! ds the-actor)
   (push-script! ds the-actor
-                (lambda () (for [(a (actor-adhoc-assertions the-actor))] (retract! the-actor a))))
+                (lambda () (for [(a (in-set (actor-adhoc-assertions the-actor)))]
+                             (retract! the-actor a))))
   (let ((f (actor-root-facet the-actor)))
     (when f
       (let abort-facet! ((f f))
@@ -436,7 +437,7 @@
 
     ;; Run stop-scripts after terminating children. This means that
     ;; children's stop-scripts run before ours.
-    (for [(script (reverse (facet-stop-scripts f)))]
+    (for [(script (in-list (reverse (facet-stop-scripts f))))]
       (schedule-script! ds
                         ac
                         (lambda ()