diff --git a/includes/libs/objectcache/BagOStuff.php b/includes/libs/objectcache/BagOStuff.php
index a2337caa8e82b..7280302e8f3ec 100644
--- a/includes/libs/objectcache/BagOStuff.php
+++ b/includes/libs/objectcache/BagOStuff.php
@@ -184,7 +184,7 @@ public function __construct( array $params = [] ) {
 	 *
 	 * @return void
 	 */
-	public function setLogger( LoggerInterface $logger ) {
+	public function setLogger( LoggerInterface $logger ): void {
 		$this->logger = $logger;
 	}