diff --git a/includes/title/Title.php b/includes/title/Title.php
index 15b60f7e8b3..0aa9ce80b63 100644
--- a/includes/title/Title.php
+++ b/includes/title/Title.php
@@ -82,6 +82,12 @@ class Title implements Stringable, LinkTarget, PageIdentity {
 	/** @var MapCacheLRU|null */
 	private static $titleCache = null;
 
+	/**
+	 * Cached instance of the main page title, to speed up isMainPage() checks.
+	 * @var Title|null
+	 */
+	private static ?Title $cachedMainPage = null;
+
 	/**
 	 * Title::newFromText maintains a cache to avoid expensive re-normalization of
 	 * commonly used titles. On a batch operation this can become a memory leak
@@ -1383,10 +1389,8 @@ class Title implements Stringable, LinkTarget, PageIdentity {
 	 * @return bool
 	 */
 	public function isMainPage() {
-		/** @var Title|null */
-		static $cachedMainPage;
-		$cachedMainPage ??= self::newMainPage();
-		return $this->equals( $cachedMainPage );
+		self::$cachedMainPage ??= self::newMainPage();
+		return $this->equals( self::$cachedMainPage );
 	}
 
 	/**
@@ -2693,6 +2697,9 @@ class Title implements Stringable, LinkTarget, PageIdentity {
 		$linkCache = MediaWikiServices::getInstance()->getLinkCache();
 		$linkCache->clear();
 
+		// Reset cached main page instance (T395214).
+		self::$cachedMainPage = null;
+
 		$titleCache = self::getTitleCache();
 		$titleCache->clear();
 	}
diff --git a/tests/phpunit/MediaWikiIntegrationTestCase.php b/tests/phpunit/MediaWikiIntegrationTestCase.php
index 05873a58ba2..07f0159bbaa 100644
--- a/tests/phpunit/MediaWikiIntegrationTestCase.php
+++ b/tests/phpunit/MediaWikiIntegrationTestCase.php
@@ -541,6 +541,9 @@ abstract class MediaWikiIntegrationTestCase extends PHPUnit\Framework\TestCase {
 		MediaWiki\Session\SessionManager::resetCache();
 
 		TestUserRegistry::clear();
+
+		// Invalidate any Title objects cached by newFromText() or isMainPage() (T395214).
+		Title::clearCaches();
 	}
 
 	/**