diff --git a/RELEASE-NOTES-1.43 b/RELEASE-NOTES-1.43
index 5f52da89def..fd3fbcf0e6d 100644
--- a/RELEASE-NOTES-1.43
+++ b/RELEASE-NOTES-1.43
@@ -140,6 +140,8 @@ because of Phabricator reports.
 
 === Other changes in 1.43 ===
 
+* Class aliases to support the old PHPUnit 4 style un-namespaced `PHPUnit_`
+  classes (such as PHPUnit_Framework_Error) have been removed.
 * …
 
 == Compatibility ==
diff --git a/tests/common/TestsAutoLoader.php b/tests/common/TestsAutoLoader.php
index a84a7eb6326..ca957307849 100644
--- a/tests/common/TestsAutoLoader.php
+++ b/tests/common/TestsAutoLoader.php
@@ -1,8 +1,5 @@
 <?php
 
-use PHPUnit\Framework\DataProviderTestSuite;
-use PHPUnit\Framework\Error\Error;
-
 /**
  * AutoLoader for the testing suite.
  *
@@ -349,32 +346,3 @@ $wgAutoloadClasses += [
 	'SuiteEventsTrait' => "$testDir/phpunit/suites/SuiteEventsTrait.php",
 ];
 // phpcs:enable
-
-/**
- * Alias any PHPUnit 4 era PHPUnit_... class
- * to its PHPUnit 6 replacement. For most classes
- * this is a direct _ -> \ replacement, but for
- * some others we might need to maintain a manual
- * mapping. Once we drop support for PHPUnit 4 this
- * should be considered deprecated and eventually removed.
- */
-spl_autoload_register( static function ( $class ) {
-	if ( !str_starts_with( $class, 'PHPUnit_' ) ) {
-		// Skip if it doesn't start with the old prefix
-		return;
-	}
-
-	// Classes that don't map 100%
-	$map = [
-		'PHPUnit_Framework_TestSuite_DataProvider' => DataProviderTestSuite::class,
-		'PHPUnit_Framework_Error' => Error::class,
-	];
-
-	$newForm = $map[$class] ?? str_replace( '_', '\\', $class );
-
-	if ( class_exists( $newForm ) || interface_exists( $newForm ) ) {
-		// If the new class name exists, alias
-		// the old name to it.
-		class_alias( $newForm, $class );
-	}
-} );