diff --git a/spec.bs b/spec.bs
index d5b75cc..b2a03dc 100644
--- a/spec.bs
+++ b/spec.bs
@@ -208,13 +208,13 @@ interface Observable {
   Observable flatMap(Mapper mapper);
 
   // Promise-returning operators.
-  Promise<sequence<any>> toArray(optional PromiseOptions options);
-  Promise<undefined> forEach(Visitor callback, optional PromiseOptions options);
-  Promise<boolean> every(Predicate predicate, optional PromiseOptions options);
-  // Maybe? Promise<any> first(optional PromiseOptions options);
-  Promise<any> find(Predicate predicate, optional PromiseOptions options);
-  Promise<boolean> some(Predicate predicate, optional PromiseOptions options);
-  Promise<any> reduce(Reducer reducer, optional any initialValue, optional PromiseOptions options);
+  Promise<sequence<any>> toArray(optional PromiseOptions options = {});
+  Promise<undefined> forEach(Visitor callback, optional PromiseOptions options = {});
+  Promise<boolean> every(Predicate predicate, optional PromiseOptions options = {});
+  // Maybe? Promise<any> first(optional PromiseOptions options = {});
+  Promise<any> find(Predicate predicate, optional PromiseOptions options = {});
+  Promise<boolean> some(Predicate predicate, optional PromiseOptions options = {});
+  Promise<any> reduce(Reducer reducer, optional any initialValue, optional PromiseOptions options = {});
 };
 </xmp>