diff --git a/libraries/config.values.php b/libraries/config.values.php
index 80640109d6..272883e1b9 100644
--- a/libraries/config.values.php
+++ b/libraries/config.values.php
@@ -32,7 +32,7 @@ $cfg_db['Servers'] = array(
         'only_db'      => 'array'
     )
 );
-$cfg_db['RecodingEngine'] = array('auto', 'iconv', 'recode', 'none');
+$cfg_db['RecodingEngine'] = array('auto', 'iconv', 'recode', 'mb', 'none');
 $cfg_db['OBGzip'] = array('auto', true, false);
 $cfg_db['MemoryLimit'] = 'short_string';
 $cfg_db['NavigationLogoLinkWindow'] = array('main', 'new');
diff --git a/libraries/config/FormDisplay.class.php b/libraries/config/FormDisplay.class.php
index c552440040..f7bd81ae7e 100644
--- a/libraries/config/FormDisplay.class.php
+++ b/libraries/config/FormDisplay.class.php
@@ -766,6 +766,13 @@ class FormDisplay
                     'recode', 'recode'
                 );
             }
+            if (!function_exists('mb_convert_encoding')) {
+                $opts['values']['mb'] .= ' (' . __('unavailable') . ')';
+                $comment .= ($comment ? ", " : '') . sprintf(
+                    __('"%s" requires %s extension'),
+                    'mb', 'mbstring'
+                );
+            }
             $opts['comment'] = $comment;
             $opts['comment_warning'] = true;
         }