diff --git a/testing/web-platform/tests/interfaces/IndexedDB.idl b/testing/web-platform/tests/interfaces/IndexedDB.idl
index f2625ebe53dd..a8ef47e89ab7 100644
--- a/testing/web-platform/tests/interfaces/IndexedDB.idl
+++ b/testing/web-platform/tests/interfaces/IndexedDB.idl
@@ -29,7 +29,7 @@ interface IDBOpenDBRequest : IDBRequest {
 };
 
 [Exposed=(Window,Worker),
- Constructor(DOMString type, optional IDBVersionChangeEventInit eventInitDict)]
+ Constructor(DOMString type, optional IDBVersionChangeEventInit eventInitDict = {})]
 interface IDBVersionChangeEvent : Event {
   readonly attribute unsigned long long oldVersion;
   readonly attribute unsigned long long? newVersion;
@@ -70,8 +70,9 @@ interface IDBDatabase : EventTarget {
                                          optional IDBTransactionMode mode = "readonly");
   void close();
 
-  [NewObject] IDBObjectStore createObjectStore(DOMString name,
-                                               optional IDBObjectStoreParameters options);
+  [NewObject] IDBObjectStore createObjectStore(
+    DOMString name,
+    optional IDBObjectStoreParameters options = {});
   void deleteObjectStore(DOMString name);
 
   // Event handlers:
@@ -115,7 +116,7 @@ interface IDBObjectStore {
 
   [NewObject] IDBIndex createIndex(DOMString name,
                                    (DOMString or sequence<DOMString>) keyPath,
-                                   optional IDBIndexParameters options);
+                                   optional IDBIndexParameters options = {});
   void deleteIndex(DOMString name);
 };