diff --git a/spring-pulsar/src/test/java/org/springframework/pulsar/listener/DefaultPulsarMessageListenerContainerTests.java b/spring-pulsar/src/test/java/org/springframework/pulsar/listener/DefaultPulsarMessageListenerContainerTests.java
index add287ac..1db59dcc 100644
--- a/spring-pulsar/src/test/java/org/springframework/pulsar/listener/DefaultPulsarMessageListenerContainerTests.java
+++ b/spring-pulsar/src/test/java/org/springframework/pulsar/listener/DefaultPulsarMessageListenerContainerTests.java
@@ -277,7 +277,8 @@ class DefaultPulsarMessageListenerContainerTests implements PulsarTestContainerS
 		DeadLetterPolicy deadLetterPolicy = DeadLetterPolicy.builder().maxRedeliverCount(1)
 				.deadLetterTopic("dpmlct-016-dlq-topic").build();
 		Map<String, Object> config = Map.of("topicNames", Collections.singleton("dpmlct-016"), "subscriptionName",
-				"dpmlct-sb-016", "ackTimeoutMillis", 1, "deadLetterPolicy", deadLetterPolicy);
+				"dpmlct-sb-016", "negativeAckRedeliveryDelayMicros", TimeUnit.SECONDS.toMicros(1), "deadLetterPolicy",
+				deadLetterPolicy);
 
 		PulsarClient pulsarClient = PulsarClient.builder().serviceUrl(PulsarTestContainerSupport.getPulsarBrokerUrl())
 				.build();
@@ -332,7 +333,8 @@ class DefaultPulsarMessageListenerContainerTests implements PulsarTestContainerS
 		DeadLetterPolicy deadLetterPolicy = DeadLetterPolicy.builder().maxRedeliverCount(5).deadLetterTopic("dlq-topic")
 				.build();
 		Map<String, Object> config = Map.of("topicNames", Collections.singleton("dpmlct-017"), "subscriptionName",
-				"dpmlct-sb-016", "ackTimeoutMillis", 1, "deadLetterPolicy", deadLetterPolicy);
+				"dpmlct-sb-016", "negativeAckRedeliveryDelayMicros", TimeUnit.SECONDS.toMicros(1), "deadLetterPolicy",
+				deadLetterPolicy);
 
 		PulsarClient pulsarClient = PulsarClient.builder().serviceUrl(PulsarTestContainerSupport.getPulsarBrokerUrl())
 				.build();
diff --git a/spring-pulsar/src/test/java/org/springframework/pulsar/listener/PulsarListenerTests.java b/spring-pulsar/src/test/java/org/springframework/pulsar/listener/PulsarListenerTests.java
index 05b255b0..22c67204 100644
--- a/spring-pulsar/src/test/java/org/springframework/pulsar/listener/PulsarListenerTests.java
+++ b/spring-pulsar/src/test/java/org/springframework/pulsar/listener/PulsarListenerTests.java
@@ -298,7 +298,7 @@ public class PulsarListenerTests implements PulsarTestContainerSupport {
 	@ContextConfiguration(classes = AckTimeoutkRedeliveryBackoffTest.AckTimeoutRedeliveryConfig.class)
 	class AckTimeoutkRedeliveryBackoffTest {
 
-		static CountDownLatch ackTimeoutRedeliveryBackoffLatch = new CountDownLatch(5);
+		static CountDownLatch ackTimeoutRedeliveryBackoffLatch = new CountDownLatch(3);
 
 		@Test
 		void pulsarListenerWithAckTimeoutRedeliveryBackoff() throws Exception {
@@ -310,19 +310,29 @@ public class PulsarListenerTests implements PulsarTestContainerSupport {
 		@Configuration
 		static class AckTimeoutRedeliveryConfig {
 
+			/**
+			 * The following PulsarListener is for testing the ack timeout settings. We
+			 * set an ack timeout of 1 second in the listener and then will not ack the
+			 * incoming message unless the tracking CountDownLatch count goes down to
+			 * zero. This means that there were enough ack timeouts and corresponding
+			 * redeliveries of the same message. Note that we are doing a manual ack
+			 * because we want to ack the message only when the latch count becomes zero.
+			 */
 			@PulsarListener(id = "withAckTimeoutRedeliveryBackoff",
 					subscriptionName = "withAckTimeoutRedeliveryBackoffSubscription",
 					topics = "withAckTimeoutRedeliveryBackoff-test-topic",
-					ackTimeoutRedeliveryBackoff = "ackTimeoutRedeliveryBackoff",
+					ackTimeoutRedeliveryBackoff = "ackTimeoutRedeliveryBackoff", ackMode = AckMode.MANUAL,
 					subscriptionType = SubscriptionType.Shared, properties = { "ackTimeoutMillis=1000" })
-			void listen(String ignored) {
+			void listen(String ignored, Acknowledgement acknowledgement) {
 				ackTimeoutRedeliveryBackoffLatch.countDown();
-				throw new RuntimeException();
+				if (ackTimeoutRedeliveryBackoffLatch.getCount() == 0) {
+					acknowledgement.acknowledge();
+				}
 			}
 
 			@Bean
 			public RedeliveryBackoff ackTimeoutRedeliveryBackoff() {
-				return MultiplierRedeliveryBackoff.builder().minDelayMs(1000).maxDelayMs(5 * 1000).multiplier(2)
+				return MultiplierRedeliveryBackoff.builder().minDelayMs(1000).maxDelayMs(3 * 1000).multiplier(2)
 						.build();
 			}
 
@@ -394,7 +404,8 @@ public class PulsarListenerTests implements PulsarTestContainerSupport {
 
 			@PulsarListener(id = "deadLetterPolicyListener", subscriptionName = "deadLetterPolicySubscription",
 					topics = "dlpt-topic-1", deadLetterPolicy = "deadLetterPolicy",
-					subscriptionType = SubscriptionType.Shared, properties = { "ackTimeoutMillis=1000" })
+					subscriptionType = SubscriptionType.Shared,
+					properties = { "negativeAckRedeliveryDelayMicros=1000000" })
 			void listen(String msg) {
 				latch.countDown();
 				throw new RuntimeException("fail " + msg);