diff --git a/module/spring-boot-amqp/src/main/java/org/springframework/boot/amqp/docker/compose/RabbitEnvironment.java b/module/spring-boot-amqp/src/main/java/org/springframework/boot/amqp/docker/compose/RabbitEnvironment.java
index bc776b015db..0fa34bc1524 100644
--- a/module/spring-boot-amqp/src/main/java/org/springframework/boot/amqp/docker/compose/RabbitEnvironment.java
+++ b/module/spring-boot-amqp/src/main/java/org/springframework/boot/amqp/docker/compose/RabbitEnvironment.java
@@ -35,8 +35,14 @@ class RabbitEnvironment {
 	private final @Nullable String password;
 
 	RabbitEnvironment(Map<String, @Nullable String> env) {
-		this.username = env.getOrDefault("RABBITMQ_DEFAULT_USER", env.getOrDefault("RABBITMQ_USERNAME", "guest"));
-		this.password = env.getOrDefault("RABBITMQ_DEFAULT_PASS", env.getOrDefault("RABBITMQ_PASSWORD", "guest"));
+		this.username = extract(env, "RABBITMQ_DEFAULT_USER", "RABBITMQ_USERNAME");
+		this.password = extract(env, "RABBITMQ_DEFAULT_PASS", "RABBITMQ_PASSWORD");
+	}
+
+	private static String extract(Map<String, @Nullable String> env, String key, String fallbackKey) {
+		String value = env.get(key);
+		value = (value != null) ? value : env.get(fallbackKey);
+		return (value != null) ? value : "guest";
 	}
 
 	@Nullable String getUsername() {
diff --git a/module/spring-boot-amqp/src/test/java/org/springframework/boot/amqp/docker/compose/RabbitEnvironmentTests.java b/module/spring-boot-amqp/src/test/java/org/springframework/boot/amqp/docker/compose/RabbitEnvironmentTests.java
index 1ecb0b4d6ff..734e5cc4ae0 100644
--- a/module/spring-boot-amqp/src/test/java/org/springframework/boot/amqp/docker/compose/RabbitEnvironmentTests.java
+++ b/module/spring-boot-amqp/src/test/java/org/springframework/boot/amqp/docker/compose/RabbitEnvironmentTests.java
@@ -17,8 +17,10 @@
 package org.springframework.boot.amqp.docker.compose;
 
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.Map;
 
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -69,4 +71,29 @@ class RabbitEnvironmentTests {
 		assertThat(environment.getPassword()).isEqualTo("secret");
 	}
 
+	@Test
+	void getUsernameWhenRabbitmqDefaultUserHasNoValue() {
+		Map<String, @Nullable String> env = new HashMap<>();
+		env.put("RABBITMQ_DEFAULT_USER", null);
+		RabbitEnvironment environment = new RabbitEnvironment(env);
+		assertThat(environment.getUsername()).isEqualTo("guest");
+	}
+
+	@Test
+	void getPasswordWhenRabbitmqDefaultPassHasNoValue() {
+		Map<String, @Nullable String> env = new HashMap<>();
+		env.put("RABBITMQ_DEFAULT_PASS", null);
+		RabbitEnvironment environment = new RabbitEnvironment(env);
+		assertThat(environment.getPassword()).isEqualTo("guest");
+	}
+
+	@Test
+	void getUsernameWhenRabbitmqDefaultUserHasNoValueAndHasRabbitmqUsername() {
+		Map<String, @Nullable String> env = new HashMap<>();
+		env.put("RABBITMQ_DEFAULT_USER", null);
+		env.put("RABBITMQ_USERNAME", "me");
+		RabbitEnvironment environment = new RabbitEnvironment(env);
+		assertThat(environment.getUsername()).isEqualTo("me");
+	}
+
 }