diff --git a/.phan/config.php b/.phan/config.php
index 0fdefe054d5..a12e1293405 100644
--- a/.phan/config.php
+++ b/.phan/config.php
@@ -26,10 +26,6 @@ $cfg['file_list'] = array_merge(
 	function_exists( 'wikidiff2_do_diff' ) ? [] : [ '.phan/stubs/wikidiff.php' ],
 	class_exists( PEAR::class ) ? [] : [ '.phan/stubs/mail.php' ],
 	defined( 'PASSWORD_ARGON2I' ) ? [] : [ '.phan/stubs/password.php' ],
-	// Per composer.json, PHPUnit 6 is used for PHP 7.0+, PHPUnit 4 otherwise.
-	// Load the interface for the version of PHPUnit that isn't installed.
-	// Phan only supports PHP 7.0+ (and not HHVM), so we only need to stub PHPUnit 4.
-	class_exists( PHPUnit_TextUI_Command::class ) ? [] : [ '.phan/stubs/phpunit4.php' ],
 	class_exists( ProfilerExcimer::class ) ? [] : [ '.phan/stubs/excimer.php' ],
 	[
 		// This makes constants and globals known to Phan before processing all other files.
diff --git a/.phan/stubs/phpunit4.php b/.phan/stubs/phpunit4.php
deleted file mode 100644
index e5e88e6bab1..00000000000
--- a/.phan/stubs/phpunit4.php
+++ /dev/null
@@ -1,11 +0,0 @@
-<?php
-
-/**
- * Some old classes from PHPUnit 4 that MediaWiki (conditionally) references.
- *
- * phpcs:ignoreFile
- */
-
-class PHPUnit_TextUI_Command {
-
-}
diff --git a/RELEASE-NOTES-1.35 b/RELEASE-NOTES-1.35
index 07d86a6f188..50f89b539d5 100644
--- a/RELEASE-NOTES-1.35
+++ b/RELEASE-NOTES-1.35
@@ -46,7 +46,6 @@ For notes on 1.34.x and older releases, see HISTORY.
 === New developer features in 1.35 ===
 * …
 
-
 === External library changes in 1.35 ===
 * …
 
@@ -79,6 +78,9 @@ because of Phabricator reports.
 * …
 
 === Deprecations in 1.35 ===
+* The PHPUnit4And6Compat class, used to provide compatibility with PHPUnit 4, is
+  now deprecated. MediaWiki support for PHPUnit 4 ended with the removal of HHVM
+  support.
 * …
 
 === Other changes in 1.35 ===
diff --git a/composer.json b/composer.json
index c92898bcfbc..9eac7469563 100644
--- a/composer.json
+++ b/composer.json
@@ -72,7 +72,7 @@
 		"nikic/php-parser": "3.1.5",
 		"seld/jsonlint": "1.7.1",
 		"nmred/kafka-php": "0.1.5",
-		"phpunit/phpunit": "4.8.36 || ^6.5",
+		"phpunit/phpunit": "^6.5",
 		"psy/psysh": "0.9.9",
 		"wikimedia/avro": "1.9.0",
 		"wikimedia/testing-access-wrapper": "~1.0",
diff --git a/maintenance/checkLess.php b/maintenance/checkLess.php
index 62d6680c3f4..df8e9405596 100644
--- a/maintenance/checkLess.php
+++ b/maintenance/checkLess.php
@@ -53,12 +53,11 @@ class CheckLess extends Maintenance {
 			define( 'MW_PHPUNIT_TEST', true );
 		}
 
-		$textUICommand = new PHPUnit_TextUI_Command();
+		$textUICommand = new \PHPUnit\TextUI\Command();
 		$argv = [
 			"$IP/tests/phpunit/phpunit.php",
 			"$IP/tests/phpunit/suites/LessTestSuite.php"
 		];
-		// @phan-suppress-next-line PhanUndeclaredMethod
 		$textUICommand->run( $argv );
 	}
 }
diff --git a/tests/phpunit/PHPUnit4And6Compat.php b/tests/phpunit/PHPUnit4And6Compat.php
index 1ef0c916839..bfcb987f5cf 100644
--- a/tests/phpunit/PHPUnit4And6Compat.php
+++ b/tests/phpunit/PHPUnit4And6Compat.php
@@ -20,6 +20,7 @@
 
 /**
  * @since 1.31
+ * @deprecated since 1.35; we don't support PHPUnit 4 any more
  */
 trait PHPUnit4And6Compat {
 	/**