diff --git a/smoke-test/spring-boot-smoke-test-config/src/main/java/smoketest/config/FromEnvConfigurationProperties.java b/smoke-test/spring-boot-smoke-test-config/src/main/java/smoketest/config/FromEnvConfigurationProperties.java
index 69ba779e3b3..a4dce8eaa6f 100644
--- a/smoke-test/spring-boot-smoke-test-config/src/main/java/smoketest/config/FromEnvConfigurationProperties.java
+++ b/smoke-test/spring-boot-smoke-test-config/src/main/java/smoketest/config/FromEnvConfigurationProperties.java
@@ -16,18 +16,20 @@
 
 package smoketest.config;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.context.properties.ConfigurationProperties;
 
 @ConfigurationProperties("from-env")
 class FromEnvConfigurationProperties {
 
-	private String key1;
+	private @Nullable String key1;
 
-	String getKey1() {
+	@Nullable String getKey1() {
 		return this.key1;
 	}
 
-	void setKey1(String key1) {
+	void setKey1(@Nullable String key1) {
 		this.key1 = key1;
 	}
 
diff --git a/smoke-test/spring-boot-smoke-test-config/src/main/java/smoketest/config/package-info.java b/smoke-test/spring-boot-smoke-test-config/src/main/java/smoketest/config/package-info.java
new file mode 100644
index 00000000000..a80ecd91890
--- /dev/null
+++ b/smoke-test/spring-boot-smoke-test-config/src/main/java/smoketest/config/package-info.java
@@ -0,0 +1,20 @@
+/*
+ * Copyright 2012-present the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+@NullMarked
+package smoketest.config;
+
+import org.jspecify.annotations.NullMarked;