diff --git a/lib/Doctrine/ORM/Sequencing/BigIntegerIdentityGenerator.php b/lib/Doctrine/ORM/Sequencing/BigIntegerIdentityGenerator.php
index 63373fb088c..2e169fded3e 100644
--- a/lib/Doctrine/ORM/Sequencing/BigIntegerIdentityGenerator.php
+++ b/lib/Doctrine/ORM/Sequencing/BigIntegerIdentityGenerator.php
@@ -25,7 +25,7 @@ class BigIntegerIdentityGenerator implements Generator
      *                                  to obtain the last generated identifier within the current
      *                                  database session/connection, if any.
      */
-    public function __construct($sequenceName = null)
+    public function __construct(?string $sequenceName = null)
     {
         $this->sequenceName = $sequenceName;
     }
@@ -33,7 +33,7 @@ public function __construct($sequenceName = null)
     /**
      * {@inheritdoc}
      */
-    public function generate(EntityManagerInterface $em, $entity)
+    public function generate(EntityManagerInterface $em, ?object $entity)
     {
         return (string) $em->getConnection()->lastInsertId($this->sequenceName);
     }
@@ -41,7 +41,7 @@ public function generate(EntityManagerInterface $em, $entity)
     /**
      * {@inheritdoc}
      */
-    public function isPostInsertGenerator()
+    public function isPostInsertGenerator() : bool
     {
         return true;
     }
diff --git a/lib/Doctrine/ORM/Sequencing/Generator.php b/lib/Doctrine/ORM/Sequencing/Generator.php
index 8431bbe94ac..4a5f1a34b43 100644
--- a/lib/Doctrine/ORM/Sequencing/Generator.php
+++ b/lib/Doctrine/ORM/Sequencing/Generator.php
@@ -11,11 +11,9 @@ interface Generator
     /**
      * Generates an identifier for an entity.
      *
-     * @param object $entity
-     *
-     * @return \Generator
+     * @return string|int
      */
-    public function generate(EntityManagerInterface $em, $entity);
+    public function generate(EntityManagerInterface $em, ?object $entity);
 
     /**
      * Gets whether this generator is a post-insert generator which means that
@@ -24,8 +22,6 @@ public function generate(EntityManagerInterface $em, $entity);
      *
      * By default, this method returns FALSE. Generators that have this requirement
      * must override this method and return TRUE.
-     *
-     * @return bool
      */
-    public function isPostInsertGenerator();
+    public function isPostInsertGenerator() : bool;
 }
diff --git a/lib/Doctrine/ORM/Sequencing/IdentityGenerator.php b/lib/Doctrine/ORM/Sequencing/IdentityGenerator.php
index e029716ae8a..aa4c0e96cd9 100644
--- a/lib/Doctrine/ORM/Sequencing/IdentityGenerator.php
+++ b/lib/Doctrine/ORM/Sequencing/IdentityGenerator.php
@@ -25,7 +25,7 @@ class IdentityGenerator implements Generator
      *                                  to obtain the last generated identifier within the current
      *                                  database session/connection, if any.
      */
-    public function __construct($sequenceName = null)
+    public function __construct(?string $sequenceName = null)
     {
         $this->sequenceName = $sequenceName;
     }
@@ -33,7 +33,7 @@ public function __construct($sequenceName = null)
     /**
      * {@inheritDoc}
      */
-    public function generate(EntityManagerInterface $em, $entity)
+    public function generate(EntityManagerInterface $em, ?object $entity)
     {
         return (int) $em->getConnection()->lastInsertId($this->sequenceName);
     }
@@ -41,7 +41,7 @@ public function generate(EntityManagerInterface $em, $entity)
     /**
      * {@inheritdoc}
      */
-    public function isPostInsertGenerator()
+    public function isPostInsertGenerator() : bool
     {
         return true;
     }
diff --git a/lib/Doctrine/ORM/Sequencing/Planning/ColumnValueGeneratorExecutor.php b/lib/Doctrine/ORM/Sequencing/Planning/ColumnValueGeneratorExecutor.php
index 0d79b672338..404be4fd0c8 100644
--- a/lib/Doctrine/ORM/Sequencing/Planning/ColumnValueGeneratorExecutor.php
+++ b/lib/Doctrine/ORM/Sequencing/Planning/ColumnValueGeneratorExecutor.php
@@ -25,7 +25,7 @@ public function __construct(LocalColumnMetadata $column, Generator $generator)
     /**
      * @return mixed[]
      */
-    public function execute(EntityManagerInterface $entityManager, /*object*/ $entity) : array
+    public function execute(EntityManagerInterface $entityManager, object $entity) : array
     {
         $value = $this->generator->generate($entityManager, $entity);
 
diff --git a/lib/Doctrine/ORM/Sequencing/Planning/CompositeValueGenerationPlan.php b/lib/Doctrine/ORM/Sequencing/Planning/CompositeValueGenerationPlan.php
index 7cf91505fa1..2397e1efdf7 100644
--- a/lib/Doctrine/ORM/Sequencing/Planning/CompositeValueGenerationPlan.php
+++ b/lib/Doctrine/ORM/Sequencing/Planning/CompositeValueGenerationPlan.php
@@ -25,7 +25,7 @@ public function __construct(ClassMetadata $metadata, array $executors)
         $this->executors = $executors;
     }
 
-    public function executeImmediate(EntityManagerInterface $entityManager, /*object*/ $entity) : void
+    public function executeImmediate(EntityManagerInterface $entityManager, object $entity) : void
     {
         foreach ($this->executors as $executor) {
             if ($executor->isDeferred()) {
@@ -36,7 +36,7 @@ public function executeImmediate(EntityManagerInterface $entityManager, /*object
         }
     }
 
-    public function executeDeferred(EntityManagerInterface $entityManager, /*object*/ $entity) : void
+    public function executeDeferred(EntityManagerInterface $entityManager, object $entity) : void
     {
         foreach ($this->executors as $executor) {
             if (! $executor->isDeferred()) {
@@ -47,8 +47,11 @@ public function executeDeferred(EntityManagerInterface $entityManager, /*object*
         }
     }
 
-    private function dispatchExecutor(ValueGenerationExecutor $executor, /*object*/ $entity, EntityManagerInterface $entityManager) : void
-    {
+    private function dispatchExecutor(
+        ValueGenerationExecutor $executor,
+        object $entity,
+        EntityManagerInterface $entityManager
+    ) : void {
         foreach ($executor->execute($entityManager, $entity) as $columnName => $value) {
             // TODO LocalColumnMetadata are currently shadowed and only exposed as FieldMetadata
             /** @var FieldMetadata $column */
diff --git a/lib/Doctrine/ORM/Sequencing/Planning/NoopValueGenerationPlan.php b/lib/Doctrine/ORM/Sequencing/Planning/NoopValueGenerationPlan.php
index 75a73153f57..053fc29cadd 100644
--- a/lib/Doctrine/ORM/Sequencing/Planning/NoopValueGenerationPlan.php
+++ b/lib/Doctrine/ORM/Sequencing/Planning/NoopValueGenerationPlan.php
@@ -8,12 +8,12 @@
 
 class NoopValueGenerationPlan implements ValueGenerationPlan
 {
-    public function executeImmediate(EntityManagerInterface $entityManager, /*object*/ $entity) : void
+    public function executeImmediate(EntityManagerInterface $entityManager, object $entity) : void
     {
         // no-op
     }
 
-    public function executeDeferred(EntityManagerInterface $entityManager, /*object*/ $entity) : void
+    public function executeDeferred(EntityManagerInterface $entityManager, object $entity) : void
     {
         // no-op
     }
diff --git a/lib/Doctrine/ORM/Sequencing/Planning/SingleValueGenerationPlan.php b/lib/Doctrine/ORM/Sequencing/Planning/SingleValueGenerationPlan.php
index 5dbbb2a64fe..02323a28d56 100644
--- a/lib/Doctrine/ORM/Sequencing/Planning/SingleValueGenerationPlan.php
+++ b/lib/Doctrine/ORM/Sequencing/Planning/SingleValueGenerationPlan.php
@@ -22,20 +22,21 @@ public function __construct(ClassMetadata $class, ValueGenerationExecutor $execu
         $this->executor = $executor;
     }
 
-    public function executeImmediate(EntityManagerInterface $entityManager, /*object*/ $entity) : void
+    public function executeImmediate(EntityManagerInterface $entityManager, object $entity) : void
     {
         if (! $this->executor->isDeferred()) {
             $this->dispatchExecutor($entity, $entityManager);
         }
     }
 
-    public function executeDeferred(EntityManagerInterface $entityManager, /*object*/ $entity) : void
+    public function executeDeferred(EntityManagerInterface $entityManager, object $entity) : void
     {
         if ($this->executor->isDeferred()) {
             $this->dispatchExecutor($entity, $entityManager);
         }
     }
-    private function dispatchExecutor($entity, EntityManagerInterface $entityManager) : void
+
+    private function dispatchExecutor(object $entity, EntityManagerInterface $entityManager) : void
     {
         foreach ($this->executor->execute($entityManager, $entity) as $columnName => $value) {
             // TODO LocalColumnMetadata are currently shadowed and only exposed as FieldMetadata
diff --git a/lib/Doctrine/ORM/Sequencing/Planning/ValueGenerationExecutor.php b/lib/Doctrine/ORM/Sequencing/Planning/ValueGenerationExecutor.php
index 635e95651fa..73fe8a4786d 100644
--- a/lib/Doctrine/ORM/Sequencing/Planning/ValueGenerationExecutor.php
+++ b/lib/Doctrine/ORM/Sequencing/Planning/ValueGenerationExecutor.php
@@ -11,7 +11,7 @@ interface ValueGenerationExecutor
     /**
      * @return mixed[]
      */
-    public function execute(EntityManagerInterface $entityManager, /*object*/ $entity) : array;
+    public function execute(EntityManagerInterface $entityManager, object $entity) : array;
 
     public function isDeferred() : bool;
 }
diff --git a/lib/Doctrine/ORM/Sequencing/Planning/ValueGenerationPlan.php b/lib/Doctrine/ORM/Sequencing/Planning/ValueGenerationPlan.php
index fff9006d21e..5634f085901 100644
--- a/lib/Doctrine/ORM/Sequencing/Planning/ValueGenerationPlan.php
+++ b/lib/Doctrine/ORM/Sequencing/Planning/ValueGenerationPlan.php
@@ -8,9 +8,9 @@
 
 interface ValueGenerationPlan
 {
-    public function executeImmediate(EntityManagerInterface $entityManager, /*object*/ $entity) : void;
+    public function executeImmediate(EntityManagerInterface $entityManager, object $entity) : void;
 
-    public function executeDeferred(EntityManagerInterface $entityManager, /*object*/ $entity) : void;
+    public function executeDeferred(EntityManagerInterface $entityManager, object $entity) : void;
 
     public function containsDeferred() : bool;
 }
diff --git a/lib/Doctrine/ORM/Sequencing/SequenceGenerator.php b/lib/Doctrine/ORM/Sequencing/SequenceGenerator.php
index 3f9485632c6..d15039d210d 100644
--- a/lib/Doctrine/ORM/Sequencing/SequenceGenerator.php
+++ b/lib/Doctrine/ORM/Sequencing/SequenceGenerator.php
@@ -38,13 +38,7 @@ class SequenceGenerator implements Generator, Serializable
      */
     private $maxValue;
 
-    /**
-     * Initializes a new sequence generator.
-     *
-     * @param string $sequenceName   The name of the sequence.
-     * @param int    $allocationSize The allocation size of the sequence.
-     */
-    public function __construct($sequenceName, $allocationSize)
+    public function __construct(string $sequenceName, int $allocationSize)
     {
         $this->sequenceName   = $sequenceName;
         $this->allocationSize = $allocationSize;
@@ -53,7 +47,7 @@ public function __construct($sequenceName, $allocationSize)
     /**
      * {@inheritdoc}
      */
-    public function generate(EntityManagerInterface $em, $entity)
+    public function generate(EntityManagerInterface $em, ?object $entity)
     {
         if ($this->maxValue === null || $this->nextValue === $this->maxValue) {
             // Allocate new values
@@ -70,33 +64,26 @@ public function generate(EntityManagerInterface $em, $entity)
 
     /**
      * Gets the maximum value of the currently allocated bag of values.
-     *
-     * @return int|null
      */
-    public function getCurrentMaxValue()
+    public function getCurrentMaxValue() : ?int
     {
         return $this->maxValue;
     }
 
     /**
      * Gets the next value that will be returned by generate().
-     *
-     * @return int
      */
-    public function getNextValue()
+    public function getNextValue() : int
     {
         return $this->nextValue;
     }
 
-    /**
-     * @return string
-     */
-    public function serialize()
+    public function serialize() : string
     {
         return serialize(
             [
-            'allocationSize' => $this->allocationSize,
-            'sequenceName'   => $this->sequenceName,
+                'allocationSize' => $this->allocationSize,
+                'sequenceName'   => $this->sequenceName,
             ]
         );
     }
@@ -104,7 +91,7 @@ public function serialize()
     /**
      * @param string $serialized
      */
-    public function unserialize($serialized)
+    public function unserialize($serialized) : void
     {
         $array = unserialize($serialized);
 
@@ -115,7 +102,7 @@ public function unserialize($serialized)
     /**
      * {@inheritdoc}
      */
-    public function isPostInsertGenerator()
+    public function isPostInsertGenerator() : bool
     {
         return false;
     }
diff --git a/lib/Doctrine/ORM/Sequencing/TableGenerator.php b/lib/Doctrine/ORM/Sequencing/TableGenerator.php
index 04988f04883..165b94aeb82 100644
--- a/lib/Doctrine/ORM/Sequencing/TableGenerator.php
+++ b/lib/Doctrine/ORM/Sequencing/TableGenerator.php
@@ -36,12 +36,7 @@ class TableGenerator implements Generator
      */
     private $maxValue;
 
-    /**
-     * @param string $tableName
-     * @param string $sequenceName
-     * @param int    $allocationSize
-     */
-    public function __construct($tableName, $sequenceName = 'default', $allocationSize = 10)
+    public function __construct(string $tableName, string $sequenceName = 'default', int $allocationSize = 10)
     {
         $this->tableName      = $tableName;
         $this->sequenceName   = $sequenceName;
@@ -51,7 +46,7 @@ public function __construct($tableName, $sequenceName = 'default', $allocationSi
     /**
      * {@inheritdoc}
      */
-    public function generate(EntityManagerInterface $em, $entity)
+    public function generate(EntityManagerInterface $em, ?object $entity)
     {
         if ($this->maxValue === null || $this->nextValue === $this->maxValue) {
             // Allocate new values
@@ -91,7 +86,7 @@ public function generate(EntityManagerInterface $em, $entity)
     /**
      * {@inheritdoc}
      */
-    public function isPostInsertGenerator()
+    public function isPostInsertGenerator() : bool
     {
         return false;
     }
diff --git a/lib/Doctrine/ORM/Sequencing/UuidGenerator.php b/lib/Doctrine/ORM/Sequencing/UuidGenerator.php
index 6feeb54b0e3..b27fa10d86d 100644
--- a/lib/Doctrine/ORM/Sequencing/UuidGenerator.php
+++ b/lib/Doctrine/ORM/Sequencing/UuidGenerator.php
@@ -14,7 +14,7 @@ class UuidGenerator implements Generator
     /**
      * {@inheritdoc}
      */
-    public function generate(EntityManagerInterface $em, $entity)
+    public function generate(EntityManagerInterface $em, ?object $entity)
     {
         $conn = $em->getConnection();
         $sql  = 'SELECT ' . $conn->getDatabasePlatform()->getGuidExpression();
@@ -25,7 +25,7 @@ public function generate(EntityManagerInterface $em, $entity)
     /**
      * {@inheritdoc}
      */
-    public function isPostInsertGenerator()
+    public function isPostInsertGenerator() : bool
     {
         return false;
     }
diff --git a/tests/Doctrine/Tests/Mocks/SequenceMock.php b/tests/Doctrine/Tests/Mocks/SequenceMock.php
index d06ccdba337..151f062be33 100644
--- a/tests/Doctrine/Tests/Mocks/SequenceMock.php
+++ b/tests/Doctrine/Tests/Mocks/SequenceMock.php
@@ -20,7 +20,7 @@ class SequenceMock extends SequenceGenerator
     /**
      * {@inheritdoc}
      */
-    public function generate(EntityManagerInterface $em, $entity)
+    public function generate(EntityManagerInterface $em, ?object $entity)
     {
         return $this->sequenceNumber++;
     }
diff --git a/tests/Doctrine/Tests/ORM/Functional/Ticket/GH5804Test.php b/tests/Doctrine/Tests/ORM/Functional/Ticket/GH5804Test.php
index 15b820785e9..5fed3824763 100644
--- a/tests/Doctrine/Tests/ORM/Functional/Ticket/GH5804Test.php
+++ b/tests/Doctrine/Tests/ORM/Functional/Ticket/GH5804Test.php
@@ -47,7 +47,7 @@ final class GH5804Generator implements Generator
     /**
      * {@inheritdoc}
      */
-    public function generate(EntityManagerInterface $em, $entity)
+    public function generate(EntityManagerInterface $em, ?object $entity)
     {
         return 'test5804';
     }
@@ -55,7 +55,7 @@ public function generate(EntityManagerInterface $em, $entity)
     /**
      * {@inheritdoc}
      */
-    public function isPostInsertGenerator()
+    public function isPostInsertGenerator() : bool
     {
         return false;
     }
@@ -100,7 +100,7 @@ class GH5804Article
      * @ORM\Id
      * @ORM\Column(type="GH5804Type")
      * @ORM\GeneratedValue(strategy="CUSTOM")
-     * @ORM\CustomIdGenerator(class=\Doctrine\Tests\ORM\Functional\Ticket\GH5804Generator::class)
+     * @ORM\CustomIdGenerator(class=GH5804Generator::class)
      */
     public $id;
 
diff --git a/tests/Doctrine/Tests/ORM/Mapping/ClassMetadataFactoryTest.php b/tests/Doctrine/Tests/ORM/Mapping/ClassMetadataFactoryTest.php
index 9436fc95f09..cd5613c6ca7 100644
--- a/tests/Doctrine/Tests/ORM/Mapping/ClassMetadataFactoryTest.php
+++ b/tests/Doctrine/Tests/ORM/Mapping/ClassMetadataFactoryTest.php
@@ -510,14 +510,14 @@ class CustomIdGenerator implements Generator
     /**
      * {@inheritdoc}
      */
-    public function generate(EntityManagerInterface $em, $entity): \Generator
+    public function generate(EntityManagerInterface $em, ?object $entity)
     {
     }
 
     /**
      * {@inheritdoc}
      */
-    public function isPostInsertGenerator()
+    public function isPostInsertGenerator() : bool
     {
         return false;
     }