diff --git a/plugins/woocommerce/tests/php/src/Internal/Admin/Orders/MetaBoxes/SourceAttributionTest.php b/plugins/woocommerce/tests/php/src/Internal/Admin/Orders/MetaBoxes/SourceAttributionTest.php
index d08b3ebe0f2..3bfdf6b79c9 100644
--- a/plugins/woocommerce/tests/php/src/Internal/Admin/Orders/MetaBoxes/SourceAttributionTest.php
+++ b/plugins/woocommerce/tests/php/src/Internal/Admin/Orders/MetaBoxes/SourceAttributionTest.php
@@ -14,6 +14,11 @@ use WP_UnitTestCase;
  */
 class SourceAttributionTest extends WP_UnitTestCase {
 
+	/**
+	 * System under test.
+	 *
+	 * @var SourceAttribution
+	 */
 	private $sut;
 
 	/**