diff --git a/core/Migrations/Version13000Date20170718121200.php b/core/Migrations/Version13000Date20170718121200.php
index 218497668f..dc59d43e81 100644
--- a/core/Migrations/Version13000Date20170718121200.php
+++ b/core/Migrations/Version13000Date20170718121200.php
@@ -122,6 +122,15 @@ class Version13000Date20170718121200 extends SimpleMigrationStep {
 			$table->addIndex(['root_id'], 'mounts_root_index');
 			$table->addIndex(['mount_id'], 'mounts_mount_id_index');
 			$table->addUniqueIndex(['user_id', 'root_id'], 'mounts_user_root_index');
+		} else {
+			$table = $schema->getTable('mounts');
+			$table->addColumn('mount_id', Types::BIGINT, [
+				'notnull' => false,
+				'length' => 20,
+			]);
+			if (!$table->hasIndex('mounts_mount_id_index')) {
+				$table->addIndex(['mount_id'], 'mounts_mount_id_index');
+			}
 		}
 
 		if (!$schema->hasTable('mimetypes')) {