diff --git a/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/autoconfigure/HazelcastClientConfigAvailableCondition.java b/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/autoconfigure/HazelcastClientConfigAvailableCondition.java
index 6f3ca62e7e3..e64616991e2 100644
--- a/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/autoconfigure/HazelcastClientConfigAvailableCondition.java
+++ b/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/autoconfigure/HazelcastClientConfigAvailableCondition.java
@@ -22,12 +22,14 @@ import java.net.URL;
 
 import com.hazelcast.client.config.ClientConfigRecognizer;
 import com.hazelcast.config.ConfigStream;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.boot.autoconfigure.condition.ConditionMessage.Builder;
 import org.springframework.boot.autoconfigure.condition.ConditionOutcome;
 import org.springframework.context.annotation.ConditionContext;
 import org.springframework.core.io.Resource;
 import org.springframework.core.type.AnnotatedTypeMetadata;
+import org.springframework.util.Assert;
 
 /**
  * {@link HazelcastConfigResourceCondition} that checks if the
@@ -56,8 +58,10 @@ class HazelcastClientConfigAvailableCondition extends HazelcastConfigResourceCon
 
 	static class HazelcastClientValidation {
 
-		static ConditionOutcome clientConfigOutcome(ConditionContext context, String propertyName, Builder builder) {
+		static @Nullable ConditionOutcome clientConfigOutcome(ConditionContext context, String propertyName,
+				Builder builder) {
 			String resourcePath = context.getEnvironment().getProperty(propertyName);
+			Assert.state(resourcePath != null, "'resourcePath' must not be null");
 			Resource resource = context.getResourceLoader().getResource(resourcePath);
 			if (!resource.exists()) {
 				return ConditionOutcome.noMatch(builder.because("Hazelcast configuration does not exist"));
diff --git a/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/autoconfigure/HazelcastProperties.java b/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/autoconfigure/HazelcastProperties.java
index f84e2d78ac4..066ae54369e 100644
--- a/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/autoconfigure/HazelcastProperties.java
+++ b/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/autoconfigure/HazelcastProperties.java
@@ -16,6 +16,8 @@
 
 package org.springframework.boot.hazelcast.autoconfigure;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.context.properties.ConfigurationProperties;
 import org.springframework.core.io.Resource;
 import org.springframework.util.Assert;
@@ -32,13 +34,13 @@ public class HazelcastProperties {
 	/**
 	 * The location of the configuration file to use to initialize Hazelcast.
 	 */
-	private Resource config;
+	private @Nullable Resource config;
 
-	public Resource getConfig() {
+	public @Nullable Resource getConfig() {
 		return this.config;
 	}
 
-	public void setConfig(Resource config) {
+	public void setConfig(@Nullable Resource config) {
 		this.config = config;
 	}
 
@@ -48,13 +50,13 @@ public class HazelcastProperties {
 	 * @throws IllegalArgumentException if the config attribute is set to an unknown
 	 * location
 	 */
-	public Resource resolveConfigLocation() {
-		if (this.config == null) {
+	public @Nullable Resource resolveConfigLocation() {
+		Resource config = this.config;
+		if (config == null) {
 			return null;
 		}
-		Assert.state(this.config.exists(),
-				() -> "Hazelcast configuration does not exist '" + this.config.getDescription() + "'");
-		return this.config;
+		Assert.state(config.exists(), () -> "Hazelcast configuration does not exist '" + config.getDescription() + "'");
+		return config;
 	}
 
 }
diff --git a/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/autoconfigure/health/package-info.java b/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/autoconfigure/health/package-info.java
index 3394f8ece1d..3517c53835f 100644
--- a/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/autoconfigure/health/package-info.java
+++ b/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/autoconfigure/health/package-info.java
@@ -17,4 +17,7 @@
 /**
  * Auto-configuration for Hazelcast health.
  */
+@NullMarked
 package org.springframework.boot.hazelcast.autoconfigure.health;
+
+import org.jspecify.annotations.NullMarked;
diff --git a/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/autoconfigure/package-info.java b/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/autoconfigure/package-info.java
index 115a4bd8a7e..8adb0d14c72 100644
--- a/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/autoconfigure/package-info.java
+++ b/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/autoconfigure/package-info.java
@@ -17,4 +17,7 @@
 /**
  * Auto-configuration for Hazelcast.
  */
+@NullMarked
 package org.springframework.boot.hazelcast.autoconfigure;
+
+import org.jspecify.annotations.NullMarked;
diff --git a/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/docker/compose/HazelcastEnvironment.java b/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/docker/compose/HazelcastEnvironment.java
index c4b8de9d8a4..23dec3fd390 100644
--- a/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/docker/compose/HazelcastEnvironment.java
+++ b/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/docker/compose/HazelcastEnvironment.java
@@ -18,6 +18,8 @@ package org.springframework.boot.hazelcast.docker.compose;
 
 import java.util.Map;
 
+import org.jspecify.annotations.Nullable;
+
 /**
  * Hazelcast environment details.
  *
@@ -25,13 +27,13 @@ import java.util.Map;
  */
 class HazelcastEnvironment {
 
-	private final String clusterName;
+	private final @Nullable String clusterName;
 
 	HazelcastEnvironment(Map<String, String> env) {
 		this.clusterName = env.get("HZ_CLUSTERNAME");
 	}
 
-	String getClusterName() {
+	@Nullable String getClusterName() {
 		return this.clusterName;
 	}
 
diff --git a/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/docker/compose/package-info.java b/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/docker/compose/package-info.java
index 56ac991268b..90192284f18 100644
--- a/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/docker/compose/package-info.java
+++ b/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/docker/compose/package-info.java
@@ -17,4 +17,7 @@
 /**
  * Support for Docker Compose Hazelcast service connections.
  */
+@NullMarked
 package org.springframework.boot.hazelcast.docker.compose;
+
+import org.jspecify.annotations.NullMarked;
diff --git a/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/health/package-info.java b/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/health/package-info.java
index c53637913d9..5dc6078e8a7 100644
--- a/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/health/package-info.java
+++ b/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/health/package-info.java
@@ -17,4 +17,7 @@
 /**
  * Health integration for Hazelcast.
  */
+@NullMarked
 package org.springframework.boot.hazelcast.health;
+
+import org.jspecify.annotations.NullMarked;
diff --git a/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/testcontainers/package-info.java b/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/testcontainers/package-info.java
index ce4dd161033..0947a3960dd 100644
--- a/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/testcontainers/package-info.java
+++ b/module/spring-boot-hazelcast/src/main/java/org/springframework/boot/hazelcast/testcontainers/package-info.java
@@ -17,4 +17,7 @@
 /**
  * Support for testcontainers Hazelcast service connections.
  */
+@NullMarked
 package org.springframework.boot.hazelcast.testcontainers;
+
+import org.jspecify.annotations.NullMarked;