diff --git a/syndicate/test/core/republish-wildcard-observe.rkt b/syndicate/test/core/republish-wildcard-observe.rkt
new file mode 100644
index 0000000..14351ff
--- /dev/null
+++ b/syndicate/test/core/republish-wildcard-observe.rkt
@@ -0,0 +1,14 @@
+#lang syndicate
+;;; SPDX-License-Identifier: LGPL-3.0-or-later
+;;; SPDX-FileCopyrightText: Copyright © 2022 Tony Garnock-Jones <tonyg@leastfixedpoint.com>
+
+(module+ test
+  (standard-actor-system (ds)
+    ;; The goal of this test is to make sure redundant Observe
+    ;; assertions aren't wrongly repeatedly entered into the index.
+    ;; The Rust implementation suffered from this problem for a while.
+    (spawn
+      #:daemon? #t
+      (at ds (during $x
+               (log-info "Saw: ~v" x)
+               (assert x))))))