diff --git a/tests/Util/Database/StaticDatabase.php b/tests/Util/Database/StaticDatabase.php
index 213d8a4392..a6b2575f59 100644
--- a/tests/Util/Database/StaticDatabase.php
+++ b/tests/Util/Database/StaticDatabase.php
@@ -70,7 +70,7 @@ class StaticDatabase extends Database
 	 *
 	 * @return bool
 	 */
-	public function transaction()
+	public function transaction(): bool
 	{
 		if (!$this->in_transaction && !$this->connection->beginTransaction()) {
 			return false;