diff --git a/tests/mock/filesystem_extension_manager.php b/tests/mock/filesystem_extension_manager.php
index 3332e2b82d..c5a51bbb3f 100644
--- a/tests/mock/filesystem_extension_manager.php
+++ b/tests/mock/filesystem_extension_manager.php
@@ -26,6 +26,7 @@ class phpbb_mock_filesystem_extension_manager extends phpbb_mock_extension_manag
 				$extensions[$name] = $extension;
 			}
 		}
+		ksort($extensions);
 		parent::__construct($phpbb_root_path, $extensions);
 	}
 }