diff --git a/lib/private/DB/PostgreSqlMigrator.php b/lib/private/DB/PostgreSqlMigrator.php
index 73e295705dafb..92a0842e1a739 100644
--- a/lib/private/DB/PostgreSqlMigrator.php
+++ b/lib/private/DB/PostgreSqlMigrator.php
@@ -42,7 +42,7 @@ protected function getDiff(Schema $targetSchema, \Doctrine\DBAL\Connection $conn
 					}
 					$fromDefault = $column->fromColumn->getDefault();
 					$toDefault = $column->column->getDefault();
-					$fromDefault = trim($fromDefault, "()");
+					$fromDefault = trim((string) $fromDefault, '()');
 
 					// by intention usage of !=
 					return $fromDefault != $toDefault;