diff --git a/tests/AtomFeedTest.php b/tests/AtomFeedTest.php
index 716ca6e..1daf9c7 100644
--- a/tests/AtomFeedTest.php
+++ b/tests/AtomFeedTest.php
@@ -65,8 +65,8 @@ protected function setUp(): void
     {
         parent::setUp();
         Config::modify()->set(Director::class, 'alternate_base_url', '/');
-        if (!self::$original_host) {
-            self::$original_host = $_SERVER['HTTP_HOST'];
+        if (!AtomFeedTest::$original_host) {
+            AtomFeedTest::$original_host = $_SERVER['HTTP_HOST'];
         }
         $_SERVER['HTTP_HOST'] = 'www.example.org';
     }
@@ -75,6 +75,6 @@ protected function tearDown(): void
     {
         parent::tearDown();
         Config::modify()->set(Director::class, 'alternate_base_url', null);
-        $_SERVER['HTTP_HOST'] = self::$original_host;
+        $_SERVER['HTTP_HOST'] = AtomFeedTest::$original_host;
     }
 }