diff --git a/register_participants.inc.php b/register_participants.inc.php
index 9b7551e0..1da08a53 100644
--- a/register_participants.inc.php
+++ b/register_participants.inc.php
@@ -450,7 +450,7 @@ function addRegistration($userId){
 		return "register_participants.inc.php::addRegistration -> user not found";
 	}
 
-	if($row['registrations_id'] != null){
+	if(!$row['registrations_id']){
 		return "register_participants.inc.php::addRegistration -> user already has a project registered";
 	}