diff --git a/docs/guide/db-active-record.md b/docs/guide/db-active-record.md
index 7a08c9fc00..13e04630f7 100644
--- a/docs/guide/db-active-record.md
+++ b/docs/guide/db-active-record.md
@@ -1625,7 +1625,7 @@ class Customer extends \yii\db\ActiveRecord
             return null; // this avoid calling a query searching for null primary keys
         }
         
-        return $this->ordersAggregation[0]['counted'];
+        return empty($this->ordersAggregation) ? 0 : $this->ordersAggregation[0]['counted'];
     }
 
     /**