diff --git a/module/VuFind/tests/unit-tests/src/VuFindTest/Content/Covers/BrowZineTest.php b/module/VuFind/tests/unit-tests/src/VuFindTest/Content/Covers/BrowZineTest.php
index 20c1486c337..f87dbdfd838 100644
--- a/module/VuFind/tests/unit-tests/src/VuFindTest/Content/Covers/BrowZineTest.php
+++ b/module/VuFind/tests/unit-tests/src/VuFindTest/Content/Covers/BrowZineTest.php
@@ -66,7 +66,7 @@ public static function coverProvider(): array
      * Test cover loading
      *
      * @param array       $ids      Array of IDs to look up
-     * @param ?string     $fixture  Fixture to return from backend
+     * @param ?string     $fixture  Fixture to return from backend (null to assume backend will not be called)
      * @param string|bool $expected Expected cover URL
      *
      * @return void