diff --git a/bbs/write_update.php b/bbs/write_update.php
index 878616c3e..b6db2e699 100644
--- a/bbs/write_update.php
+++ b/bbs/write_update.php
@@ -15,7 +15,12 @@ if($board['bo_use_category']) {
         $categories = array_map('trim', explode("|", $board['bo_category_list'].($is_admin ? '|공지' : '')));
         if(!empty($categories) && !in_array($ca_name, $categories))
             $msg[] = '분류를 올바르게 입력하세요.';
+
+        if(empty($categories))
+            $ca_name = '';
     }
+} else {
+    $ca_name = '';
 }
 
 $wr_subject = '';