diff --git a/web/template/syzoj/problem.php b/web/template/syzoj/problem.php
index 0e3d8ce..c61d6b3 100644
--- a/web/template/syzoj/problem.php
+++ b/web/template/syzoj/problem.php
@@ -122,7 +122,8 @@ if ($pr_flag) {
     function trans_md($str)
     {
       $s = $str;
-      if (strpos($s, "class='md") !== false)  // 没找到，那就加上
+      if (strpos($s, "class='md") === false &&
+          strpos($s, "class=\"md") === false)  // 没找到，那就加上
         $s = "<span class='md'>" . $s . "</span>";
       $s = bbcode_to_html($s);
       return $s;