diff --git a/lib/os/class.ISPConfigDebianOS.inc.php b/lib/os/class.ISPConfigDebianOS.inc.php
index 309971d27cbb89ca0ccfaa9955f4b7a500590496..533f0f4eddfb0771d1f6689fc7eb48bd24b2bda1 100644
--- a/lib/os/class.ISPConfigDebianOS.inc.php
+++ b/lib/os/class.ISPConfigDebianOS.inc.php
@@ -1152,7 +1152,7 @@ mailman-unsubscribe:  "|/var/lib/mailman/mail/mailman unsubscribe mailman"';
 			}
 		}
 		if($found === false) {
-			fseek($fp, SEEK_END);
+			fseek($fp, 0, SEEK_END);
 			fwrite($fp, "\n\n" . $add_content);
 		}
 		fclose($fp);