diff --git a/index.html b/index.html
index a40f96c..7376f26 100644
--- a/index.html
+++ b/index.html
@@ -552,6 +552,11 @@
The subscribe method when invoked MUST run the following steps:
+ - If the [=relevant global object=] of [=this=] does not have [=transient activation=],
+ return [=a promise rejected with=] with a {{"NotAllowedError"}} {{DOMException}}.
+
+ - [=Consume user activation=] of [=this=]'s [=relevant global object=].
+
- Let |promise| be a new promise.
- Return |promise| and continue the following steps asynchronously.