diff --git a/admin/environment.xml b/admin/environment.xml
index b6854547a30..cbbe57a73cc 100644
--- a/admin/environment.xml
+++ b/admin/environment.xml
@@ -112,6 +112,11 @@
           <ON_CHECK message="opensslrecommended" />
         </FEEDBACK>
       </PHP_EXTENSION>
+      <PHP_EXTENSION name="tokenizer" level="optional">
+        <FEEDBACK>
+          <ON_CHECK message="tokenizerrecommended" />
+        </FEEDBACK>
+      </PHP_EXTENSION>
     </PHP_EXTENSIONS>
   </MOODLE>
 </COMPATIBILITY_MATRIX>
diff --git a/lang/en_utf8/admin.php b/lang/en_utf8/admin.php
index 898bc73242a..893e7178939 100644
--- a/lang/en_utf8/admin.php
+++ b/lang/en_utf8/admin.php
@@ -516,6 +516,7 @@ $string['timezone'] = 'Default timezone';
 $string['timezoneforced'] = 'This is forced by the site administrator';
 $string['timezoneisforcedto'] = 'Force all users to use';
 $string['timezonenotforced'] = 'Users can choose their own timezone';
+$string['tokenizerrecommended'] = 'Installing the optional PHP Tokenizer extension is recommended -- it improves Moodle Networking functionality.';
 $string['unbookmarkthispage'] = 'unbookmark this page';
 $string['unicodeupgradenotice'] = 'In Moodle 1.6 we have migrated all languages to Unicode.  To complete the upgrade for this site, you need to convert all the data in your database to Unicode (UTF-8) using our migration script.  <a href=\"utfdbmigrate.php\">Click here to run the migration script now</a>!';
 $string['unicoderecommended'] = 'Storing all your data in Unicode (UTF-8) is recommended. New installations should be performed into databases that have their default character set as Unicode.  If you are upgrading, you should perform the UTF-8 migration process (see the Admin page).';