diff --git a/server/plugins-available/maildeliver_plugin.inc.php b/server/plugins-available/maildeliver_plugin.inc.php
index e3799d716e2f78149b113b7f96ce2bb2daab8575..c8fc0694b2235ebe1833c16dd381fd81c82c076b 100644
--- a/server/plugins-available/maildeliver_plugin.inc.php
+++ b/server/plugins-available/maildeliver_plugin.inc.php
@@ -130,6 +130,7 @@ class maildeliver_plugin {
 			$tpl->setLoop('ccloop', $tmp_addresses_arr);
 
 			// Custom filters
+			if($data["new"]["custom_mailfilter"] == 'NULL') $data["new"]["custom_mailfilter"] = '';
 			$tpl->setVar('custom_mailfilter', $data["new"]["custom_mailfilter"]);
 
 			// Move junk