diff --git a/types/quill/quill-tests.ts b/types/quill/quill-tests.ts
index b16c90b384..eba77f8b68 100644
--- a/types/quill/quill-tests.ts
+++ b/types/quill/quill-tests.ts
@@ -170,7 +170,7 @@ function test_addContainer()
 
 function test_on_EventType1(){
     var quillEditor = new Quill('#editor');
-    quillEditor.on('text-change', (newDelta, oldDelta, source)=>{
+    quillEditor.on('text-change', <T>(newDelta: T, oldDelta: T, source: string)=>{
         // happened
     });