diff --git a/smoke-test/spring-boot-smoke-test-session-data-mongodb-webflux/build.gradle b/smoke-test/spring-boot-smoke-test-session-data-mongodb-webflux/build.gradle
index 336266d8cda..1529d8b87d0 100644
--- a/smoke-test/spring-boot-smoke-test-session-data-mongodb-webflux/build.gradle
+++ b/smoke-test/spring-boot-smoke-test-session-data-mongodb-webflux/build.gradle
@@ -35,3 +35,11 @@ dependencies {
 	dockerTestImplementation("org.testcontainers:junit-jupiter")
 	dockerTestImplementation("org.testcontainers:mongodb")
 }
+
+tasks.named("compileTestJava") {
+	options.nullability.checking = "tests"
+}
+
+tasks.named("compileDockerTestJava") {
+	options.nullability.checking = "tests"
+}
diff --git a/smoke-test/spring-boot-smoke-test-session-data-mongodb-webflux/src/dockerTest/java/smoketest/session/SampleSessionWebFluxMongoApplicationTests.java b/smoke-test/spring-boot-smoke-test-session-data-mongodb-webflux/src/dockerTest/java/smoketest/session/SampleSessionWebFluxMongoApplicationTests.java
index f7123bd28da..9999dfb3d7d 100644
--- a/smoke-test/spring-boot-smoke-test-session-data-mongodb-webflux/src/dockerTest/java/smoketest/session/SampleSessionWebFluxMongoApplicationTests.java
+++ b/smoke-test/spring-boot-smoke-test-session-data-mongodb-webflux/src/dockerTest/java/smoketest/session/SampleSessionWebFluxMongoApplicationTests.java
@@ -31,6 +31,7 @@ import org.springframework.boot.test.web.server.LocalServerPort;
 import org.springframework.boot.testcontainers.service.connection.ServiceConnection;
 import org.springframework.boot.testsupport.container.TestImage;
 import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseCookie;
 import org.springframework.web.reactive.function.client.WebClient;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -63,8 +64,11 @@ class SampleSessionWebFluxMongoApplicationTests {
 		WebClient client = this.webClientBuilder.baseUrl("http://localhost:" + this.port + "/").build();
 		client.get().header("Authorization", getBasicAuth()).exchangeToMono((response) -> {
 			assertThat(response.statusCode()).isEqualTo(HttpStatus.OK);
-			return response.bodyToMono(String.class)
-				.map((sessionId) -> Tuples.of(response.cookies().getFirst("SESSION").getValue(), sessionId));
+			return response.bodyToMono(String.class).map((sessionId) -> {
+				ResponseCookie session = response.cookies().getFirst("SESSION");
+				assertThat(session).isNotNull();
+				return Tuples.of(session.getValue(), sessionId);
+			});
 		}).flatMap((tuple) -> {
 			String sessionCookie = tuple.getT1();
 			return client.get().cookie("SESSION", sessionCookie).exchangeToMono((response) -> {