diff --git a/docs/en/cookbook/mapping-classes-to-orm-and-odm.rst b/docs/en/cookbook/mapping-classes-to-orm-and-odm.rst
index 1ed7268b58..d96ec1f6e2 100644
--- a/docs/en/cookbook/mapping-classes-to-orm-and-odm.rst
+++ b/docs/en/cookbook/mapping-classes-to-orm-and-odm.rst
@@ -1,15 +1,15 @@
 Mapping Classes to the ORM and ODM
 ==================================
 
-Because of the non intrusive design of Doctrine it is possible for you to have plain PHP classes
-that are mapped to both a relational database with the Doctrine2 Object Relational Mapper and
-MongoDB with the Doctrine MongoDB Object Document Mapper, or any other persistence layer that
+Because of the non-intrusive design of Doctrine, it is possible for you to have plain PHP classes
+that are mapped to both a relational database (with the Doctrine2 Object Relational Mapper) and
+MongoDB (with the Doctrine MongoDB Object Document Mapper), or any other persistence layer that
 implements the Doctrine Common `persistence`_ interfaces.
 
 Test Subject
 ------------
 
-For this cookbook entry we need to define a class that can be persisted to both MySQL and MongoDB.
+For this cookbook entry, we need to define a class that can be persisted to both MySQL and MongoDB.
 We'll use a ``BlogPost`` as you may want to write some generic blogging functionality that has support
 for multiple Doctrine persistence layers:
 
@@ -17,7 +17,7 @@ for multiple Doctrine persistence layers:
 
     <?php
 
-    namespace Doctrine\Blog;
+    namespace Documents\Blog;
 
     class BlogPost
     {
@@ -45,9 +45,11 @@ First define the mapping for the ORM:
 
         <?php
 
-        namespace Doctrine\Blog;
+        namespace Documents\Blog;
 
-        /** @Entity(repositoryClass="Doctrine\Blog\ORM\BlogPostRepository") */
+        use Documents\Blog\Repository\ORM\BlogPostRepository;
+
+        /** @Entity(repositoryClass=BlogPostRepository::class) */
         class BlogPost
         {
             /** @Id @Column(type="integer") */
@@ -70,20 +72,20 @@ First define the mapping for the ORM:
               xsi:schemaLocation="http://doctrine-project.org/schemas/orm/doctrine-mapping
                                   http://www.doctrine-project.org/schemas/orm/doctrine-mapping.xsd">
 
-            <entity name="Documents\BlogPost" repository-class="Doctrine\Blog\ORM\BlogPostRepository">
+            <entity name="Documents\Blog\BlogPost" repository-class="Documents\Blog\Repository\ORM\BlogPostRepository">
                 <id name="id" type="integer" />
                 <field name="name" type="string" />
                 <field name="email" type="text" />
             </entity>
         </doctrine-mapping>
 
-Now you are able to persist the ``Documents\BlogPost`` with an instance of ``EntityManager``:
+Now you are able to persist the ``Documents\Blog\BlogPost`` with an instance of ``EntityManager``:
 
 .. code-block:: php
 
     <?php
 
-    $blogPost = new BlogPost()
+    $blogPost = new BlogPost();
     $blogPost->setTitle('test');
 
     $em->persist($blogPost);
@@ -95,7 +97,7 @@ You can find the blog post:
 
     <?php
 
-    $blogPost = $em->getRepository(Documents\BlogPost::class)->findOneBy(['title' => 'test']);
+    $blogPost = $em->getRepository(BlogPost::class)->findOneBy(array('title' => 'test'));
 
 MongoDB ODM
 ~~~~~~~~~~~
@@ -108,9 +110,11 @@ Now map the same class to the Doctrine MongoDB ODM:
 
         <?php
 
-        namespace Documents;
+        namespace Documents\Blog;
+
+        use Documents\Blog\Repository\ODM\BlogPostRepository;
 
-        /** @Document(repositoryClass="Doctrine\Blog\ODM\MongoDB\BlogPostRepository") */
+        /** @Document(repositoryClass=BlogPostRepository::class) */
         class BlogPost
         {
             /** @Id */
@@ -133,8 +137,8 @@ Now map the same class to the Doctrine MongoDB ODM:
               xsi:schemaLocation="http://doctrine-project.org/schemas/orm/doctrine-mapping
                                   http://www.doctrine-project.org/schemas/orm/doctrine-mapping.xsd">
 
-            <document name="Documents\BlogPost" repository-class="Doctrine\Blog\ODM\MongoDB\BlogPostRepository">
-                <field field-name="id" type="id" />
+            <document name="Documents\Blog\BlogPost" repository-class="Documents\Blog\Repository\ODM\BlogPostRepository">
+                <id strategy="INCREMENT" type="int" />
                 <field field-name="name" type="string" />
                 <field field-name="email" type="text" />
             </document>
@@ -146,7 +150,7 @@ Now the same class is able to be persisted in the same way using an instance of
 
     <?php
 
-    $blogPost = new BlogPost()
+    $blogPost = new BlogPost();
     $blogPost->setTitle('test');
 
     $dm->persist($blogPost);
@@ -158,23 +162,39 @@ You can find the blog post:
 
     <?php
 
-    $blogPost = $dm->getRepository(Documents\BlogPost::class)->findOneBy(['title' => 'test']);
+    $blogPost = $dm->getRepository(BlogPost::class)->findOneBy(array('title' => 'test'));
 
 Repository Classes
 ------------------
 
-You can implement the same repository interface for the ORM and MongoDB ODM easily:
+You can implement the same repository interface for the ORM and MongoDB ODM easily, e.g. by creating ``BlogPostRepositoryInterface``:
 
 .. code-block:: php
 
     <?php
+    // An Interface to ensure ORM and ODM Repository classes have the same methods implemented
+
+    namespace Documents\Blog\Repository;
+
+    use Documents\Blog\BlogPost;
+
+    interface BlogPostRepositoryInterface
+    {
+        public function findPostById(int $id): ?BlogPost;
+    }
 
-    namespace Doctrine\Blog\ORM;
+Define repository methods required by the interface for the ORM:
 
-    use Doctrine\Blog\BlogPost;
+.. code-block:: php
+
+    <?php
+
+    namespace Documents\Blog\Repository\ORM;
+
+    use Documents\Blog\Repository\BlogPostRepositoryInterface;
     use Doctrine\ORM\EntityRepository;
 
-    class BlogPostRepository extends EntityRepository
+    class BlogPostRepository extends EntityRepository implements BlogPostRepositoryInterface
     {
         public function findPostById(int $id): ?BlogPost
         {
@@ -188,14 +208,14 @@ Now define the same repository methods for the MongoDB ODM:
 
     <?php
 
-    namespace Doctrine\Blog\ODM\MongoDB;
+    namespace Documents\Blog\Repository\ODM;
 
-    use Documents\BlogPost;
-    use Doctrine\ODM\MongoDB\DocumentRepository;
+    use Documents\Blog\Repository\BlogPostRepositoryInterface;
+    use Doctrine\ODM\MongoDB\Repository\DocumentRepository;
 
-    class BlogPostRepository extends DocumentRepository
+    class BlogPostRepository extends DocumentRepository implements BlogPostRepositoryInterface
     {
-        public function findPostById(string $id): ?BlogPost
+        public function findPostById(int $id): ?BlogPost
         {
             return $this->findOneBy(['id' => $id]);
         }
diff --git a/lib/Doctrine/ODM/MongoDB/Aggregation/Builder.php b/lib/Doctrine/ODM/MongoDB/Aggregation/Builder.php
index dfd17488eb..c2ff35196e 100644
--- a/lib/Doctrine/ODM/MongoDB/Aggregation/Builder.php
+++ b/lib/Doctrine/ODM/MongoDB/Aggregation/Builder.php
@@ -233,6 +233,12 @@ static function (Stage $stage) {
 
         if ($this->getStage(0) instanceof Stage\GeoNear) {
             $pipeline[0]['$geoNear']['query'] = $this->applyFilters($pipeline[0]['$geoNear']['query']);
+        } elseif ($this->getStage(0) instanceof Stage\IndexStats) {
+            // Don't apply any filters when using an IndexStats stage: since it
+            // needs to be the first pipeline stage, prepending a match stage
+            // with discriminator information will not work
+
+            return $pipeline;
         } else {
             $matchExpression = $this->applyFilters([]);
             if ($matchExpression !== []) {
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Aggregation/BuilderTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Aggregation/BuilderTest.php
index ae39926ee6..a131f1f66d 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Aggregation/BuilderTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Aggregation/BuilderTest.php
@@ -13,8 +13,10 @@
 use Documents\BlogTagAggregation;
 use Documents\CmsComment;
 use Documents\GuestServer;
+use Documents\Project;
 use Documents\Tag;
 use MongoDB\BSON\UTCDateTime;
+use function array_keys;
 
 class BuilderTest extends BaseTest
 {
@@ -343,6 +345,15 @@ public function testBuilderWithOutStageReturnsNoData()
         $this->assertCount(0, $result);
     }
 
+    public function testBuilderWithIndexStatsStageDoesNotApplyFilters()
+    {
+        $builder = $this->dm
+            ->createAggregationBuilder(Project::class)
+            ->indexStats();
+
+        $this->assertSame('$indexStats', array_keys($builder->getPipeline()[0])[0]);
+    }
+
     private function insertTestData()
     {
         $baseballTag = new Tag('baseball');