diff --git a/Kafka/ConsumerInterface.php b/Kafka/ConsumerInterface.php
index 6625b4ab..5d7922f4 100644
--- a/Kafka/ConsumerInterface.php
+++ b/Kafka/ConsumerInterface.php
@@ -16,7 +16,7 @@ interface ConsumerInterface
 	 * @param Struct $struct
 	 * @return mixed
 	 */
-	public function onHandler(Struct $struct): mixed;
+	public function onHandler(Struct $struct): void;
 
 
 }