diff --git a/tests/unit/cms/classes/CmsObjectTest.php b/tests/unit/cms/classes/CmsObjectTest.php
index 895825b5c..93d4d3753 100644
--- a/tests/unit/cms/classes/CmsObjectTest.php
+++ b/tests/unit/cms/classes/CmsObjectTest.php
@@ -6,6 +6,8 @@ use Cms\Classes\Theme;
 class TestCmsObject extends CmsObject
 {
     protected $dirName = 'testobjects';
+
+    protected $allowedExtensions = ['htm', 'html'];
 }
 
 class TestTemporaryCmsObject extends CmsObject