diff --git a/app/Models/Activity.php b/app/Models/Activity.php
index b541c59cd125..5641967634d3 100644
--- a/app/Models/Activity.php
+++ b/app/Models/Activity.php
@@ -83,6 +83,11 @@ class Activity extends Eloquent
         return $this->belongsTo('App\Models\Task')->withTrashed();
     }
 
+    public function key()
+    {
+        return sprintf('%s-%s-%s', $this->activity_type_id, $this->client_id, $this->created_at->timestamp);
+    }
+
     /**
      * @return mixed
      */
diff --git a/app/Ninja/Transformers/ActivityTransformer.php b/app/Ninja/Transformers/ActivityTransformer.php
index 9a7be6c86649..3bc22d7adc87 100644
--- a/app/Ninja/Transformers/ActivityTransformer.php
+++ b/app/Ninja/Transformers/ActivityTransformer.php
@@ -22,6 +22,7 @@ class ActivityTransformer extends EntityTransformer
     public function transform(Activity $activity)
     {
         return [
+            'id' => $activity->key(),
             'activity_type_id' => $activity->activity_type_id,
             'client_id' => $activity->client->public_id,
             'user_id' => $activity->user->public_id + 1,