diff --git a/UPGRADE.md b/UPGRADE.md
index 4cff9282884..a9dab1d0708 100644
--- a/UPGRADE.md
+++ b/UPGRADE.md
@@ -1,5 +1,14 @@
 # Upgrade to 4.0
 
+## Remove remaining `Serializable` implementation
+
+`SequenceGenerator` does not implement the `Serializable` interface anymore.
+
+The following methods have been removed:
+
+* `SequenceGenerator::serialize()`
+* `SequenceGenerator::unserialize()`
+
 ## Remove `orm:schema-tool:update` option `--complete`
 
 That option was a no-op.
diff --git a/psalm-baseline.xml b/psalm-baseline.xml
index ec624d93079..052aabe7056 100644
--- a/psalm-baseline.xml
+++ b/psalm-baseline.xml
@@ -206,11 +206,6 @@
       <code><![CDATA[$entity]]></code>
     </PossiblyNullArgument>
   </file>
-  <file src="src/Id/SequenceGenerator.php">
-    <ParamNameMismatch>
-      <code><![CDATA[$serialized]]></code>
-    </ParamNameMismatch>
-  </file>
   <file src="src/Internal/Hydration/AbstractHydrator.php">
     <ReferenceConstraintViolation>
       <code><![CDATA[return $rowData;]]></code>
diff --git a/src/Id/SequenceGenerator.php b/src/Id/SequenceGenerator.php
index 659bb58b9e4..29d34445025 100644
--- a/src/Id/SequenceGenerator.php
+++ b/src/Id/SequenceGenerator.php
@@ -5,17 +5,12 @@
 namespace Doctrine\ORM\Id;
 
 use Doctrine\DBAL\Connections\PrimaryReadReplicaConnection;
-use Doctrine\Deprecations\Deprecation;
 use Doctrine\ORM\EntityManagerInterface;
-use Serializable;
-
-use function serialize;
-use function unserialize;
 
 /**
  * Represents an ID generator that uses a database sequence.
  */
-class SequenceGenerator extends AbstractIdGenerator implements Serializable
+class SequenceGenerator extends AbstractIdGenerator
 {
     private int $nextValue     = 0;
     private int|null $maxValue = null;
@@ -66,20 +61,6 @@ public function getNextValue(): int
         return $this->nextValue;
     }
 
-    /** @deprecated without replacement. */
-    final public function serialize(): string
-    {
-        Deprecation::trigger(
-            'doctrine/orm',
-            'https://github.com/doctrine/orm/pull/11468',
-            '%s() is deprecated, use __serialize() instead. %s won\'t implement the Serializable interface anymore in ORM 4.',
-            __METHOD__,
-            self::class,
-        );
-
-        return serialize($this->__serialize());
-    }
-
     /** @return array<string, mixed> */
     public function __serialize(): array
     {
@@ -89,20 +70,6 @@ public function __serialize(): array
         ];
     }
 
-    /** @deprecated without replacement. */
-    final public function unserialize(string $serialized): void
-    {
-        Deprecation::trigger(
-            'doctrine/orm',
-            'https://github.com/doctrine/orm/pull/11468',
-            '%s() is deprecated, use __unserialize() instead. %s won\'t implement the Serializable interface anymore in ORM 4.',
-            __METHOD__,
-            self::class,
-        );
-
-        $this->__unserialize(unserialize($serialized));
-    }
-
     /** @param array<string, mixed> $data */
     public function __unserialize(array $data): void
     {