diff --git a/types/underscore.string/underscore.string-tests.ts b/types/underscore.string/underscore.string-tests.ts
index 8eed630854..545f6362d6 100644
--- a/types/underscore.string/underscore.string-tests.ts
+++ b/types/underscore.string/underscore.string-tests.ts
@@ -13,6 +13,8 @@ _.chop('whitespace', 3);
 
 _.clean(' foo    bar   ');
 
+_.cleanDiacritics('ääkkönen');
+
 _.chars('Hello');
 
 _.swapCase('hELLO');