diff --git a/src/rill/wheel.clj b/src/rill/wheel.clj
index bee654b..63fa387 100644
--- a/src/rill/wheel.clj
+++ b/src/rill/wheel.clj
@@ -331,6 +331,7 @@
   "
   (:refer-clojure :exclude [empty empty? type])
   (:require [rill.event-store :refer [retrieve-events append-events]]
+            [rill.message :as message]
             [rill.wheel.repository :as repo]
             [clojure.string :as string]
             [clojure.spec :as s]
@@ -377,6 +378,12 @@
   [aggregate]
   (::new-events aggregate))
 
+(defn aggregate?
+  "Test that `obj` is an aggregate."
+  [obj]
+  (boolean (and (::id obj)
+                (::type obj))))
+
 (defn empty
   "Create a new aggregate with id `aggregate-id` and no
   events. Aggregate version will be -1. Note that empty aggregates
@@ -586,7 +593,12 @@
   [aggregate]
   (let [events (::new-events aggregate)]
     {::status    :ok
-     ::events    events
+     ::events    (->> events
+                      (map-indexed (fn [index event]
+                                     (-> event
+                                         (assoc ::message/stream-id (::id aggregate))
+                                         (assoc ::message/number (+ (::version aggregate) (inc index))))))
+                      vec)
      ::aggregate (-> aggregate
                      (update ::version + (count events))
                      (assoc ::new-events []))}))
diff --git a/src/rill/wheel/repository.clj b/src/rill/wheel/repository.clj
index 412f9a8..36f9517 100644
--- a/src/rill/wheel/repository.clj
+++ b/src/rill/wheel/repository.clj
@@ -24,4 +24,3 @@
   "Test if `repo` is a repository"
   [repo]
   (satisfies? Repository repo))
-
diff --git a/test/rill/wheel_test.clj b/test/rill/wheel_test.clj
index 477ff65..d2d08e6 100644
--- a/test/rill/wheel_test.clj
+++ b/test/rill/wheel_test.clj
@@ -151,31 +151,38 @@
                         commit!)))
 
     (is (sub? {::aggregate/status :ok
-               ::aggregate/events [{::message/type ::installed}]}
+               ::aggregate/events [{::message/type      ::installed
+                                    ::message/stream-id {:turnstile-id    id
+                                                         ::aggregate/type ::turnstile}
+                                    ::message/number    0}]}
               (-> (get-turnstile repo id)
                   (install-turnstile)
                   commit!)))
 
     (is (sub? {::aggregate/status :ok
-               ::aggregate/events [{::message/type ::arm-pushed-ineffectively}]}
+               ::aggregate/events [{::message/type   ::arm-pushed-ineffectively
+                                    ::message/number 1}]}
               (-> (get-turnstile repo id)
                   (push-arm)
                   commit!)))
 
     (is (sub? {::aggregate/status :ok
-               ::aggregate/events [{::message/type ::coin-inserted}]}
+               ::aggregate/events [{::message/type   ::coin-inserted
+                                    ::message/number 2}]}
               (-> (get-turnstile repo id)
                   (insert-coin)
                   commit!)))
 
     (is (sub? {::aggregate/status :ok
-               ::aggregate/events [{::message/type ::arm-turned}]}
+               ::aggregate/events [{::message/type   ::arm-turned
+                                    ::message/number 3}]}
               (-> (get-turnstile repo id)
                   (push-arm)
                   commit!)))
 
     (is (sub? {::aggregate/status :ok
-               ::aggregate/events [{::message/type ::arm-pushed-ineffectively}]}
+               ::aggregate/events [{::message/type   ::arm-pushed-ineffectively
+                                    ::message/number 4}]}
               (-> (get-turnstile repo id)
                   (push-arm)
                   commit!)))))