diff --git a/tst/Data/GoogleCloudStorageTest.php b/tst/Data/GoogleCloudStorageTest.php
index 3df5719d..4e13ee2a 100644
--- a/tst/Data/GoogleCloudStorageTest.php
+++ b/tst/Data/GoogleCloudStorageTest.php
@@ -40,7 +40,7 @@ class GoogleCloudStorageTest extends TestCase
         }
     }
 
-    public static function tearDownAfterClass()
+    public static function tearDownAfterClass(): void
     {
         self::$_bucket->delete();
     }