diff --git a/imperative/distributed/federation.rkt b/imperative/distributed/federation.rkt
index c2085ac..220f27f 100644
--- a/imperative/distributed/federation.rkt
+++ b/imperative/distributed/federation.rkt
@@ -263,7 +263,9 @@
                 (define old-matches (subscription-matches sub))
                 (define old-match-holders (hash-ref old-matches captures set))
                 (define new-match-holders (set-remove old-match-holders linkid))
-                (define new-matches (hash-set old-matches captures new-match-holders))
+                (define new-matches (if (set-empty? new-match-holders)
+                                        (hash-remove old-matches captures)
+                                        (hash-set old-matches captures new-match-holders)))
                 (store-sub! (struct-copy subscription sub [matches new-matches]))
                 (match (set-count new-match-holders)
                   [0 (for [((peer peer-subid) (in-hash (subscription-holders sub)))]