diff --git a/src/infrastructure/markup/remarkup/markuprule/PhabricatorRemarkupRuleYoutube.php b/src/infrastructure/markup/remarkup/markuprule/PhabricatorRemarkupRuleYoutube.php
index 4351b95d34..b23f049580 100644
--- a/src/infrastructure/markup/remarkup/markuprule/PhabricatorRemarkupRuleYoutube.php
+++ b/src/infrastructure/markup/remarkup/markuprule/PhabricatorRemarkupRuleYoutube.php
@@ -1,59 +1,59 @@
 <?php
 
 /*
  * Copyright 2012 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *   http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 
 /**
  * @group markup
  */
 final class PhabricatorRemarkupRuleYoutube
   extends PhutilRemarkupRule {
 
   public function apply($text) {
     $this->uri = new PhutilURI($text);
 
     if ($this->uri->getDomain() &&
-        preg_match('/youtube\.com$/', $this->uri->getDomain())) {
+        preg_match('/(^|\.)youtube\.com$/', $this->uri->getDomain())) {
       return $this->markupYoutubeLink();
     }
 
     return $text;
   }
 
   public function markupYoutubeLink() {
     $v = idx($this->uri->getQueryParams(), 'v');
     if ($v) {
       $youtube_src = 'https://www.youtube.com/embed/'.$v;
       $iframe =
         '<div class="embedded-youtube-video">'.
           phutil_render_tag(
             'iframe',
             array(
               'width'       => '650',
               'height'      => '400',
               'style'       => 'margin: 1em auto; border: 0px;',
               'src'         => $youtube_src,
               'frameborder' => 0,
             ),
             '').
         '</div>';
       return $this->getEngine()->storeText($iframe);
     } else {
       return $this->uri;
     }
   }
 
 }