diff --git a/rocketmq-client/src/producer/default_mq_producer.rs b/rocketmq-client/src/producer/default_mq_producer.rs
index 0a2df6a65..92f5b9f6b 100644
--- a/rocketmq-client/src/producer/default_mq_producer.rs
+++ b/rocketmq-client/src/producer/default_mq_producer.rs
@@ -817,7 +817,7 @@ impl MQProducer for DefaultMQProducer {
         let mq = self
             .default_mqproducer_impl
             .as_mut()
-            .unwrap()
+            .ok_or(RocketMQError::not_initialized("DefaultMQProducerImpl not initialized"))?
             .invoke_message_queue_selector(
                 &msg,
                 Arc::new(selector),