diff --git a/spring-rabbit/src/main/java/org/springframework/amqp/rabbit/listener/RabbitListenerEndpoint.java b/spring-rabbit/src/main/java/org/springframework/amqp/rabbit/listener/RabbitListenerEndpoint.java
index 3a916e0b..979dd9ee 100644
--- a/spring-rabbit/src/main/java/org/springframework/amqp/rabbit/listener/RabbitListenerEndpoint.java
+++ b/spring-rabbit/src/main/java/org/springframework/amqp/rabbit/listener/RabbitListenerEndpoint.java
@@ -153,6 +153,7 @@ public interface RabbitListenerEndpoint {
 	 * @return the content type.
 	 * @since 2.3
 	 */
+	@Nullable
 	default String getReplyContentType() {
 		return null;
 	}