diff --git a/source b/source
index 980e51fd8ba..f6ab9b57977 100644
--- a/source
+++ b/source
@@ -53857,20 +53857,27 @@ interface <dfn interface>HTMLSelectElement</dfn> : <span>HTMLElement</span> {
 
   <p>If the <code>select</code> is being rendered as a <span>drop-down box</span> with <span>base
   appearance</span>, then the user agent should allow the user to <dfn
-  data-x="select-open-picker">open the picker</dfn>. Opening the picker will either fire a
-  corresponding <code data-x="event-mousedown">mousedown</code> or <code
-  data-x="event-keydown">keydown</code> event on the <code>select</code> element. Calling
-  <code data-x="dom-Event-preventDefault">preventDefault()</code> on either of these events will
-  prevent the picker from opening. Otherwise, the picker is opened.</p>
+  data-x="select-open-picker">open the picker</dfn> given a corresponding <code>select</code>
+  element <var>select</var> and a corresponding <code data-x="event-mousedown">mousedown</code> or
+  <code data-x="event-keydown">keydown</code> event <var>event</var>:
+
+  <ol>
+   <li><p>If <var>event</var>'s <span>canceled flag</span> is set, then return.</p></li>
+
+   <li><p>Run the <span>show popover</span> algorithm given <var>select</var>'s <span>select
+   popover</span>, false, and <var>select</var>.</p></li>
+  </ol>
 
   <p>If the <code>select</code> is being rendered as a <span>drop-down box</span> with <span>base
-  appearance</span>, then the user agent should allow the user to <dfn>focus another option</dfn>.
-  Performing this action will fire a corresponding <code data-x="event-keydown">keydown</code> event
-  on the currently focused <code>option</code> element, then run the <span>focusing steps</span> on
-  another <code>option</code> within the <code>select</code>. Calling <code
-  data-x="dom-Event-preventDefault">preventDefault()</code> on the <code
-  data-x="event-keydown">keydown</code> event will prevent the new <code>option</code> from being
-  focused.</p>
+  appearance</span>, then the user agent should allow the user to <dfn>focus another option</dfn>
+  given the new <code>option</code> element to focus <var>option</var> and a <code
+  data-x="event-keydown">keydown</code> event <var>event</var>:</p>
+
+  <ol>
+   <li><p>If <var>event</var>'s <span>canceled flag</span> is set, then return.</p></li>
+
+   <li><p>Run the <span>focusing steps</span> on <var>newOption</var>.</p></li>
+  </ol>
 
   <p class="note">Implementations commonly allow the user to focus the next or previous option via
   the arrow-up and arrow-down keys, focus the first or last option via the Home or End keys, or