diff --git a/dom.bs b/dom.bs
index 2f00ca5ab..56a9e8c2d 100644
--- a/dom.bs
+++ b/dom.bs
@@ -1062,15 +1062,18 @@ and an <a>event listener</a> <var>listener</var>, run these steps:
 
 <ol>
  <li>
-  <p>If <var>eventTarget</var>'s <a>relevant global object</a> is a {{ServiceWorkerGlobalScope}}
-  object and its associated <a>service worker</a>'s <a for="service worker">script resource</a>'s
-  <a for="script resource">has ever been evaluated flag</a> is set, then <a>throw</a> a
-  <code>TypeError</code>.
-  [[!SERVICE-WORKERS]]
-
-  <p class="note no-backref">To optimize storing the event types allowed for the service worker and
-  to avoid non-deterministic changes to the event listeners, invocation of the method is allowed
-  only during the very first evaluation of the service worker script.
+  <p>If <var>listener</var> observes a <a>functional event</a>, <var>eventTarget</var> is a
+  {{ServiceWorkerGlobalScope}} object, and its associated <a>service worker</a>'s <a for="service
+  worker">script resource</a>'s <a for="script resource">has ever been evaluated flag</a> is set,
+  then the user agent must show a message on a developer console that the user agent stores the event
+  <a for="event listener">type</a> of the <a>functional event</a> for the <a>service worker</a> only
+  during the very first evalution of the <a>service worker</a> script, and the asynchronously added
+  <a>functional event</a> will not start the <a>service worker</a>. [[!SERVICE-WORKERS]]
+
+  <p class="note no-backref">To optimize storing the event types allowed for the <a>service
+  worker</a>, Service Workers specification does not store the asynchronously added event <a
+  for="event listener">type</a>. The <a>event listener</a> will still be added under this condition,
+  but the implmentations have to inform developers about this behavior.
 
  <li><p>If <var>listener</var>'s <a for="event listener">callback</a> is null, then return.
 
@@ -1118,11 +1121,13 @@ and an <a>event listener</a> <var>listener</var>, set <var>listener</var>'s
 method, when invoked, must run these steps:
 
 <ol>
- <li><p>If the <a>context object</a>'s <a>relevant global object</a> is a
- {{ServiceWorkerGlobalScope}} object and its associated <a>service worker</a>'s
- <a for="service worker">script resource</a>'s
- <a for="script resource">has ever been evaluated flag</a> is set, then <a>throw</a> a
- <code>TypeError</code>. [[!SERVICE-WORKERS]]
+ <li><p>If <var>type</var> is one of the <a>functional events</a>'s <a for="event
+ listener">type</a>, the <a>context object</a> is a {{ServiceWorkerGlobalScope}} object, and its
+ associated <a>service worker</a>'s <a for="service worker">script resource</a>'s <a for="script
+ resource">has ever been evaluated flag</a> is set, then the user agent must show a message on a
+ developer console that the user agent will still start the <a>service worker</a> for the
+ <a>functional event</a> that has been stored during the very first evalution of the <a>service
+ worker</a> script and is asynchronously removed. [[!SERVICE-WORKERS]]
 
  <li><p>Let <var>capture</var> be the result of <a>flattening</a> <var>options</var>.