diff --git a/.phan/config.php b/.phan/config.php
index 5acdba32f..adff6a16b 100644
--- a/.phan/config.php
+++ b/.phan/config.php
@@ -7,6 +7,7 @@ $cfg['directory_list'] = array_merge(
 	[
 		'../../extensions/CheckUser',
 		'../../extensions/Echo',
+		'../../extensions/UserMerge',
 	]
 );
 
@@ -15,6 +16,7 @@ $cfg['exclude_analysis_directory_list'] = array_merge(
 	[
 		'../../extensions/CheckUser',
 		'../../extensions/Echo',
+		'../../extensions/UserMerge',
 	]
 );
 
diff --git a/extension.json b/extension.json
index f704f9ff2..e574ba5b0 100644
--- a/extension.json
+++ b/extension.json
@@ -396,6 +396,12 @@
 		},
 		"Echo": {
 			"class": "MediaWiki\\Extension\\AbuseFilter\\Hooks\\Handlers\\EchoHandler"
+		},
+		"UserMerge": {
+			"class": "MediaWiki\\Extension\\AbuseFilter\\Hooks\\Handlers\\UserMergeHandler",
+			"services": [
+				"MainConfig"
+			]
 		}
 	},
 	"Hooks": {
@@ -418,7 +424,7 @@
 		"CheckUserInsertChangesRow": "CheckUser",
 		"CheckUserInsertPrivateEventRow": "CheckUser",
 		"CheckUserInsertLogEventRow": "CheckUser",
-		"UserMergeAccountFields": "MediaWiki\\Extension\\AbuseFilter\\Hooks\\Handlers\\UserMergeHandler::onUserMergeAccountFields",
+		"UserMergeAccountFields": "UserMerge",
 		"BeforeCreateEchoEvent": "Echo",
 		"ParserOutputStashForEdit": "FilteredActions",
 		"UnitTestsAfterDatabaseSetup": "Tests",
diff --git a/includes/Hooks/Handlers/UserMergeHandler.php b/includes/Hooks/Handlers/UserMergeHandler.php
index 2511730ee..e57b1eba1 100644
--- a/includes/Hooks/Handlers/UserMergeHandler.php
+++ b/includes/Hooks/Handlers/UserMergeHandler.php
@@ -2,23 +2,31 @@
 
 namespace MediaWiki\Extension\AbuseFilter\Hooks\Handlers;
 
-class UserMergeHandler {
+use Config;
+use MediaWiki\Extension\UserMerge\Hooks\AccountFieldsHook;
+
+class UserMergeHandler implements AccountFieldsHook {
+
+	private Config $config;
+
+	public function __construct( Config $config ) {
+		$this->config = $config;
+	}
 
 	/**
 	 * Tables that Extension:UserMerge needs to update
-	 * @todo Use new hook system once UserMerge is updated
 	 *
-	 * @param array &$updateFields
+	 * @param array[] &$updateFields
 	 */
-	public static function onUserMergeAccountFields( array &$updateFields ) {
-		global $wgAbuseFilterActorTableSchemaMigrationStage;
+	public function onUserMergeAccountFields( array &$updateFields ) {
+		$actorStage = $this->config->get( 'AbuseFilterActorTableSchemaMigrationStage' );
 		$updateFields[] = [
 			'abuse_filter',
 			'af_user',
 			'af_user_text',
 			'batchKey' => 'af_id',
 			'actorId' => 'af_actor',
-			'actorStage' => $wgAbuseFilterActorTableSchemaMigrationStage,
+			'actorStage' => $actorStage,
 		];
 		$updateFields[] = [
 			'abuse_filter_log',
@@ -32,7 +40,7 @@ class UserMergeHandler {
 			'afh_user_text',
 			'batchKey' => 'afh_id',
 			'actorId' => 'afh_actor',
-			'actorStage' => $wgAbuseFilterActorTableSchemaMigrationStage,
+			'actorStage' => $actorStage,
 		];
 	}
 
diff --git a/tests/phpunit/integration/AbuseFilterExtensionJsonTest.php b/tests/phpunit/integration/AbuseFilterExtensionJsonTest.php
index 7fdd99815..d2f80fb5f 100644
--- a/tests/phpunit/integration/AbuseFilterExtensionJsonTest.php
+++ b/tests/phpunit/integration/AbuseFilterExtensionJsonTest.php
@@ -2,6 +2,7 @@
 
 namespace MediaWiki\Extension\AbuseFilter\Tests\Integration;
 
+use ExtensionRegistry;
 use MediaWiki\Tests\ExtensionJsonTestBase;
 
 /**
@@ -14,4 +15,12 @@ class AbuseFilterExtensionJsonTest extends ExtensionJsonTestBase {
 	/** @inheritDoc */
 	protected string $extensionJsonPath = __DIR__ . '/../../../extension.json';
 
+	public function provideHookHandlerNames(): iterable {
+		foreach ( $this->getExtensionJson()['HookHandlers'] ?? [] as $hookHandlerName => $specification ) {
+			if ( $hookHandlerName === 'UserMerge' && !ExtensionRegistry::getInstance()->isLoaded( 'UserMerge' ) ) {
+				continue;
+			}
+			yield [ $hookHandlerName ];
+		}
+	}
 }