diff --git a/include/constant.php b/include/constant.php
index 0b097eb65..84588e2d2 100644
--- a/include/constant.php
+++ b/include/constant.php
@@ -308,3 +308,4 @@ define ("SQL_LIST_UNPAID_INVOICE_DATE_LIMIT" ,"
 define ('EMAIL_LIMIT',1002);
 define ('EXC_PARAM_VALUE',1005);
 define ('EXC_PARAM_TYPE',1006);
+define ('EXC_DUPLICATE',1200);