diff --git a/web/template/syzoj/problem.php b/web/template/syzoj/problem.php
index 4ea35a3..5ae76ff 100644
--- a/web/template/syzoj/problem.php
+++ b/web/template/syzoj/problem.php
@@ -121,15 +121,11 @@ if ($pr_flag) {
     <?php
     function trans_md($str)
     {
-      return
-        "<span class='md'>" .
-        bbcode_to_html(
-          // htmlentities(
-          $str
-          // , ENT_QUOTES, 'UTF-8')
-        )
-        . "</span>"
-      ;
+      $s = $str;
+      if (strpos($s, "class='md") !== false)  // 没找到，那就加上
+        $s = "<span class='md'>" . $s ."</span>";
+      $s = bbcode_to_html($s);
+      return $s;      
     }
     ?>
     <div class="row">