diff --git a/includes/api/ApiMessageTrait.php b/includes/api/ApiMessageTrait.php
index 8d48009825d..b570afd2eaf 100644
--- a/includes/api/ApiMessageTrait.php
+++ b/includes/api/ApiMessageTrait.php
@@ -135,10 +135,6 @@ trait ApiMessageTrait {
 		$this->apiData = $data;
 	}
 
-	public function serialize(): string {
-		return serialize( $this->__serialize() );
-	}
-
 	public function __serialize() {
 		return [
 			'parent' => parent::__serialize(),
@@ -147,10 +143,6 @@ trait ApiMessageTrait {
 		];
 	}
 
-	public function unserialize( $serialized ): void {
-		$this->__unserialize( unserialize( $serialized ) );
-	}
-
 	public function __unserialize( $data ) {
 		parent::__unserialize( $data['parent'] );
 		$this->apiCode = $data['apiCode'];
diff --git a/includes/language/Message.php b/includes/language/Message.php
index 24323657a35..24e786ce129 100644
--- a/includes/language/Message.php
+++ b/includes/language/Message.php
@@ -138,7 +138,7 @@ use MediaWiki\StubObject\StubUserLang;
  * @newable
  * @ingroup Language
  */
-class Message implements MessageSpecifier, Serializable {
+class Message implements MessageSpecifier {
 	/** Use message text as-is */
 	public const FORMAT_PLAIN = 'plain';
 	/** Use normal wikitext -> HTML parsing (the result will be wrapped in a block-level HTML tag) */
@@ -252,15 +252,6 @@ class Message implements MessageSpecifier, Serializable {
 		$this->language = $language;
 	}
 
-	/**
-	 * @see Serializable::serialize()
-	 * @since 1.26
-	 * @return string
-	 */
-	public function serialize(): string {
-		return serialize( $this->__serialize() );
-	}
-
 	/**
 	 * @see Serializable::serialize()
 	 * @since 1.38
@@ -287,15 +278,6 @@ class Message implements MessageSpecifier, Serializable {
 	/**
 	 * @see Serializable::unserialize()
 	 * @since 1.38
-	 * @param string $serialized
-	 */
-	public function unserialize( $serialized ): void {
-		$this->__unserialize( unserialize( $serialized ) );
-	}
-
-	/**
-	 * @see Serializable::unserialize()
-	 * @since 1.26
 	 * @param array $data
 	 */
 	public function __unserialize( $data ) {
diff --git a/includes/libs/GenericArrayObject.php b/includes/libs/GenericArrayObject.php
index 1a0842844a8..2efe4bb5468 100644
--- a/includes/libs/GenericArrayObject.php
+++ b/includes/libs/GenericArrayObject.php
@@ -176,17 +176,6 @@ abstract class GenericArrayObject extends ArrayObject {
 		return true;
 	}
 
-	/**
-	 * @see Serializable::serialize
-	 *
-	 * @since 1.20
-	 *
-	 * @return string
-	 */
-	public function serialize(): string {
-		return serialize( $this->__serialize() );
-	}
-
 	/**
 	 * @see Serializable::serialize
 	 *
@@ -214,17 +203,6 @@ abstract class GenericArrayObject extends ArrayObject {
 		];
 	}
 
-	/**
-	 * @see Serializable::unserialize
-	 *
-	 * @since 1.20
-	 *
-	 * @param string $serialization
-	 */
-	public function unserialize( $serialization ): void {
-		$this->__unserialize( unserialize( $serialization ) );
-	}
-
 	/**
 	 * @see Serializable::unserialize
 	 *
diff --git a/includes/libs/HashRing.php b/includes/libs/HashRing.php
index 61aecf18689..1a048cbd13d 100644
--- a/includes/libs/HashRing.php
+++ b/includes/libs/HashRing.php
@@ -41,7 +41,7 @@
  *
  * @since 1.22
  */
-class HashRing implements Serializable {
+class HashRing {
 	/** @var string Hashing algorithm for hash() */
 	protected $algo;
 	/** @var int[] Non-empty (location => integer weight) */
@@ -438,10 +438,6 @@ class HashRing implements Serializable {
 		return time();
 	}
 
-	public function serialize(): string {
-		return serialize( $this->__serialize() );
-	}
-
 	public function __serialize() {
 		return [
 			'algorithm' => $this->algo,
@@ -450,13 +446,9 @@ class HashRing implements Serializable {
 		];
 	}
 
-	public function unserialize( $serialized ): void {
-		$this->__unserialize( unserialize( $serialized ) );
-	}
-
 	public function __unserialize( $data ) {
 		if ( is_array( $data ) ) {
-			$this->init( $data['locations'], $data['algorithm'], $data['ejections'] );
+			$this->init( $data['locations'] ?? [], $data['algorithm'] ?? 'sha1', $data['ejections'] ?? [] );
 		} else {
 			throw new UnexpectedValueException( __METHOD__ . ": unable to decode JSON." );
 		}
diff --git a/includes/libs/MapCacheLRU.php b/includes/libs/MapCacheLRU.php
index 15a4a287fb9..975d062c400 100644
--- a/includes/libs/MapCacheLRU.php
+++ b/includes/libs/MapCacheLRU.php
@@ -33,7 +33,7 @@ use Wikimedia\LightweightObjectStore\ExpirationAwareness;
  * @ingroup Cache
  * @since 1.23
  */
-class MapCacheLRU implements ExpirationAwareness, Serializable {
+class MapCacheLRU implements ExpirationAwareness {
 	/** @var array Map of (key => value) */
 	private $cache = [];
 	/** @var array Map of (key => (UNIX timestamp, (field => UNIX timestamp))) */
@@ -367,10 +367,6 @@ class MapCacheLRU implements ExpirationAwareness, Serializable {
 		];
 	}
 
-	public function serialize(): string {
-		return serialize( $this->__serialize() );
-	}
-
 	public function __unserialize( $data ) {
 		$this->cache = $data['entries'] ?? [];
 		$this->timestamps = $data['timestamps'] ?? [];
@@ -379,10 +375,6 @@ class MapCacheLRU implements ExpirationAwareness, Serializable {
 		$this->epoch = $this->getCurrentTime();
 	}
 
-	public function unserialize( $serialized ): void {
-		$this->__unserialize( unserialize( $serialized ) );
-	}
-
 	/**
 	 * @return float UNIX timestamp
 	 * @codeCoverageIgnore
diff --git a/includes/site/Site.php b/includes/site/Site.php
index 01f14342c53..a34a3c4b255 100644
--- a/includes/site/Site.php
+++ b/includes/site/Site.php
@@ -29,7 +29,7 @@ use MediaWiki\Site\MediaWikiPageNameNormalizer;
  * @ingroup Site
  * @author Jeroen De Dauw < jeroendedauw@gmail.com >
  */
-class Site implements Serializable {
+class Site {
 	public const TYPE_UNKNOWN = 'unknown';
 	public const TYPE_MEDIAWIKI = 'mediawiki';
 
@@ -651,17 +651,6 @@ class Site implements Serializable {
 		return new Site();
 	}
 
-	/**
-	 * @see Serializable::serialize
-	 *
-	 * @since 1.21
-	 *
-	 * @return string
-	 */
-	public function serialize(): string {
-		return serialize( $this->__serialize() );
-	}
-
 	/**
 	 * @see Serializable::serialize
 	 *
@@ -684,17 +673,6 @@ class Site implements Serializable {
 		];
 	}
 
-	/**
-	 * @see Serializable::unserialize
-	 *
-	 * @since 1.21
-	 *
-	 * @param string $serialized
-	 */
-	public function unserialize( $serialized ): void {
-		$this->__unserialize( unserialize( $serialized ) );
-	}
-
 	/**
 	 * @see Serializable::unserialize
 	 *
diff --git a/tests/phpunit/includes/MessageTest.php b/tests/phpunit/includes/MessageTest.php
index 512ebc5d989..cb01481f4cb 100644
--- a/tests/phpunit/includes/MessageTest.php
+++ b/tests/phpunit/includes/MessageTest.php
@@ -897,8 +897,8 @@ class MessageTest extends MediaWikiLangTestCase {
 	}
 
 	/**
-	 * @covers Message::serialize
-	 * @covers Message::unserialize
+	 * @covers Message::__serialize
+	 * @covers Message::__unserialize
 	 */
 	public function testSerialization() {
 		$msg = new Message( 'parentheses' );
diff --git a/tests/phpunit/includes/auth/AuthManagerTest.php b/tests/phpunit/includes/auth/AuthManagerTest.php
index 38e6d2d74d6..87aed05489e 100644
--- a/tests/phpunit/includes/auth/AuthManagerTest.php
+++ b/tests/phpunit/includes/auth/AuthManagerTest.php
@@ -162,7 +162,7 @@ class AuthManagerTest extends \MediaWikiIntegrationTestCase {
 			$name = $prop->getName();
 			$usedMsg = ltrim( "$msg ($name)" );
 			if ( $name === 'message' && $expected->message ) {
-				$this->assertSame( $expected->message->serialize(), $actual->message->serialize(),
+				$this->assertSame( $expected->message->__serialize(), $actual->message->__serialize(),
 					$usedMsg );
 			} else {
 				$this->assertEquals( $expected->$name, $actual->$name, $usedMsg );
diff --git a/tests/phpunit/includes/site/SiteImporterTest.php b/tests/phpunit/includes/site/SiteImporterTest.php
index 7ed1b0640dc..02e675d7d84 100644
--- a/tests/phpunit/includes/site/SiteImporterTest.php
+++ b/tests/phpunit/includes/site/SiteImporterTest.php
@@ -186,7 +186,7 @@ class SiteImporterTest extends MediaWikiIntegrationTestCase {
 
 		foreach ( $sites as $site ) {
 			$key = $site->getGlobalId();
-			$data = unserialize( $site->serialize() );
+			$data = unserialize( serialize( $site ) );
 
 			$serialized[$key] = $data;
 		}
diff --git a/tests/phpunit/includes/site/SiteListTest.php b/tests/phpunit/includes/site/SiteListTest.php
index 9912da69e6b..dcef807f3bf 100644
--- a/tests/phpunit/includes/site/SiteListTest.php
+++ b/tests/phpunit/includes/site/SiteListTest.php
@@ -209,7 +209,8 @@ class SiteListTest extends MediaWikiIntegrationTestCase {
 	 *
 	 * @param SiteList $list
 	 * @covers SiteList::getSerializationData
-	 * @covers SiteList::unserialize
+	 * @covers SiteList::__serialize
+	 * @covers SiteList::__unserialize
 	 */
 	public function testSerialization( SiteList $list ) {
 		$serialization = serialize( $list );
diff --git a/tests/phpunit/includes/site/SiteTest.php b/tests/phpunit/includes/site/SiteTest.php
index 1d3d753bc2f..84ef0d3e47e 100644
--- a/tests/phpunit/includes/site/SiteTest.php
+++ b/tests/phpunit/includes/site/SiteTest.php
@@ -284,12 +284,10 @@ class SiteTest extends MediaWikiIntegrationTestCase {
 	/**
 	 * @dataProvider instanceProvider
 	 * @param Site $site
-	 * @covers Site::serialize
-	 * @covers Site::unserialize
+	 * @covers Site::__serialize
+	 * @covers Site::__unserialize
 	 */
 	public function testSerialization( Site $site ) {
-		$this->assertInstanceOf( Serializable::class, $site );
-
 		$serialization = serialize( $site );
 		$newInstance = unserialize( $serialization );
 
diff --git a/tests/phpunit/unit/includes/libs/MapCacheLRUTest.php b/tests/phpunit/unit/includes/libs/MapCacheLRUTest.php
index 9020c67ce8a..66de987e400 100644
--- a/tests/phpunit/unit/includes/libs/MapCacheLRUTest.php
+++ b/tests/phpunit/unit/includes/libs/MapCacheLRUTest.php
@@ -49,8 +49,8 @@ class MapCacheLRUTest extends PHPUnit\Framework\TestCase {
 	}
 
 	/**
-	 * @covers MapCacheLRU::serialize()
-	 * @covers MapCacheLRU::unserialize()
+	 * @covers MapCacheLRU::__serialize()
+	 * @covers MapCacheLRU::__unserialize()
 	 */
 	public function testSerialize() {
 		$cache = new MapCacheLRU( 3 );