diff --git a/classes/migration/upgrade/OJSv3_3_0UpgradeMigration.inc.php b/classes/migration/upgrade/OJSv3_3_0UpgradeMigration.inc.php
index c9952cf085b..b0164df3157 100644
--- a/classes/migration/upgrade/OJSv3_3_0UpgradeMigration.inc.php
+++ b/classes/migration/upgrade/OJSv3_3_0UpgradeMigration.inc.php
@@ -178,7 +178,7 @@ private function _toJSON($row, $tableName, $searchBy, $valueToConvert)
 
 		if (!count($primaryKeys)) {
 			foreach (array_keys(get_object_vars($row)) as $column) {
-				if (substr($column, -3, '_id')) {
+				if (substr($column, -3) ==  '_id') {
 					$primaryKeys[] = $column;
 				}
 			}