diff --git a/tests/phpunit/includes/DiscussionParserTest.php b/tests/phpunit/includes/DiscussionParserTest.php
index 0b9f3c12a..ebb1a32f3 100644
--- a/tests/phpunit/includes/DiscussionParserTest.php
+++ b/tests/phpunit/includes/DiscussionParserTest.php
@@ -120,6 +120,8 @@ class EchoDiscussionParserTest extends MediaWikiTestCase {
 	protected function setUp() {
 		parent::setUp();
 
+		$this->setMwGlobals( array( 'wgDiff' => false ) );
+
 		// we only need to add these users once, we won't (can't) tear them down anyway
 		static $executed = false;
 		if ( $executed === true ) {