diff --git a/fleetd/src/test/java/dev/ltms/fleet/msg/MessageServiceTest.java b/fleetd/src/test/java/dev/ltms/fleet/msg/MessageServiceTest.java
index 6ef4dd6..5bc2732 100644
--- a/fleetd/src/test/java/dev/ltms/fleet/msg/MessageServiceTest.java
+++ b/fleetd/src/test/java/dev/ltms/fleet/msg/MessageServiceTest.java
@@ -911,6 +911,9 @@ class MessageServiceTest {
     void foreignInstanceTicketDoesNotResolve() {
         MessageService other = newIndependentInstance();
         String ticket = messages.sendAsync(T, "task on first instance", null, null);
+        // `other` must reach the same sequence number, or this test passes against an empty map
+        // instead of against a colliding id.
+        other.sendAsync(T, "task on second instance", null, null);
 
         // control: the id resolves in the instance that minted it, so a null below cannot be
         // explained by broken plumbing — only by the ticket being foreign to `other`.