diff --git a/src/symbols/exception/PhutilMissingSymbolException.php b/src/symbols/exception/PhutilMissingSymbolException.php
--- a/src/symbols/exception/PhutilMissingSymbolException.php
+++ b/src/symbols/exception/PhutilMissingSymbolException.php
@@ -5,16 +5,22 @@
   public function __construct($symbol, $type, $reason) {
     parent::__construct(
       pht(
-        "Failed to load %s '%s': %s ".
-        "If this symbol was recently added or moved, your library map may ".
-        "be out of date. You can rebuild the map by running '%s'. ".
-        "For more information, see: %s",
+        "Failed to load %s '%s': %s.\n\n".
+        "If you are not a developer, this almost always means that a library ".
+        "is out of date. For example, you may have upgraded `phabricator` ".
+        "without upgrading `libphutil`, or vice versa. It might also mean ".
+        "that you need to restart Apache or PHP-FPM. Make sure all libraries ".
+        "are up to date and all services have been restarted.\n\n".
+        "If you are a developer and this symbol was recently added or moved, ".
+        "your library map may need to be rebuilt. You can rebuild the map by ".
+        "running '%s'. For more information, see:\n\n".
+        "%s",
         $type,
         $symbol,
         $reason,
         'arc liberate',
-        'http://www.phabricator.com/docs/phabricator/article/'.
-        'libphutil_Libraries_User_Guide.html'));
+        'https://secure.phabricator.com/book/phabcontrib/article/'.
+          'adding_new_classes/'));
   }
 
 }