diff --git a/cmd/mesh-controller/builder_on_the_bus_test.go b/cmd/mesh-controller/builder_on_the_bus_test.go
index 4ab796b6..8c6afb64 100644
--- a/cmd/mesh-controller/builder_on_the_bus_test.go
+++ b/cmd/mesh-controller/builder_on_the_bus_test.go
@@ -47,6 +47,11 @@ func aBuilderOnTheBus(t *testing.T) builderOnTheBus {
 		}
 		*c.into = kv
 	}
+	// And the controller's own buckets, as its start asserts them: a merge it hears is kept in the bucket of the merges
+	// (ADR 0539 §17), which no other test need have made on this bus first.
+	if err := js.EnsureControllerBuckets(); err != nil {
+		t.Fatal(err)
+	}
 	servingBus.Store(js)
 	t.Cleanup(func() { servingBus.Store(nil) })
 	withTrunkList(t, true)