diff --git a/module/spring-boot-reactor-netty/build.gradle b/module/spring-boot-reactor-netty/build.gradle
index 55c1e0e8c0e..9ed4c281f4b 100644
--- a/module/spring-boot-reactor-netty/build.gradle
+++ b/module/spring-boot-reactor-netty/build.gradle
@@ -43,8 +43,14 @@ dependencies {
 	testImplementation("io.projectreactor:reactor-test")
 	testImplementation("org.springframework:spring-webflux")
 
+	testCompileOnly("com.google.code.findbugs:jsr305")
+
 	testRuntimeOnly("ch.qos.logback:logback-classic")
 	testRuntimeOnly("org.eclipse.jetty:jetty-client")
 	testRuntimeOnly("org.eclipse.jetty.http2:jetty-http2-client")
 	testRuntimeOnly("org.eclipse.jetty.http2:jetty-http2-client-transport")
 }
+
+tasks.named("compileTestJava") {
+	options.nullability.checking = "tests"
+}
diff --git a/module/spring-boot-reactor-netty/src/test/java/org/springframework/boot/reactor/netty/NettyReactiveWebServerFactoryTests.java b/module/spring-boot-reactor-netty/src/test/java/org/springframework/boot/reactor/netty/NettyReactiveWebServerFactoryTests.java
index d3b6136e39c..cc93043de27 100644
--- a/module/spring-boot-reactor-netty/src/test/java/org/springframework/boot/reactor/netty/NettyReactiveWebServerFactoryTests.java
+++ b/module/spring-boot-reactor-netty/src/test/java/org/springframework/boot/reactor/netty/NettyReactiveWebServerFactoryTests.java
@@ -23,6 +23,7 @@ import java.util.Arrays;
 
 import io.netty.channel.Channel;
 import org.awaitility.Awaitility;
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Disabled;
 import org.junit.jupiter.api.Test;
 import org.mockito.InOrder;
@@ -246,7 +247,7 @@ class NettyReactiveWebServerFactoryTests extends AbstractReactiveWebServerFactor
 
 		@Override
 		NettyWebServer createNettyWebServer(HttpServer httpServer, ReactorHttpHandlerAdapter handlerAdapter,
-				Duration lifecycleTimeout, Shutdown shutdown) {
+				@Nullable Duration lifecycleTimeout, Shutdown shutdown) {
 			return new NoPortNettyWebServer(httpServer, handlerAdapter, lifecycleTimeout, shutdown);
 		}
 
@@ -254,8 +255,8 @@ class NettyReactiveWebServerFactoryTests extends AbstractReactiveWebServerFactor
 
 	static class NoPortNettyWebServer extends NettyWebServer {
 
-		NoPortNettyWebServer(HttpServer httpServer, ReactorHttpHandlerAdapter handlerAdapter, Duration lifecycleTimeout,
-				Shutdown shutdown) {
+		NoPortNettyWebServer(HttpServer httpServer, ReactorHttpHandlerAdapter handlerAdapter,
+				@Nullable Duration lifecycleTimeout, @Nullable Shutdown shutdown) {
 			super(httpServer, handlerAdapter, lifecycleTimeout, shutdown, null);
 		}
 
diff --git a/module/spring-boot-reactor-netty/src/test/java/org/springframework/boot/reactor/netty/autoconfigure/NettyReactiveWebServerFactoryCustomizerTests.java b/module/spring-boot-reactor-netty/src/test/java/org/springframework/boot/reactor/netty/autoconfigure/NettyReactiveWebServerFactoryCustomizerTests.java
index f8e210bf165..c3ee9666fc5 100644
--- a/module/spring-boot-reactor-netty/src/test/java/org/springframework/boot/reactor/netty/autoconfigure/NettyReactiveWebServerFactoryCustomizerTests.java
+++ b/module/spring-boot-reactor-netty/src/test/java/org/springframework/boot/reactor/netty/autoconfigure/NettyReactiveWebServerFactoryCustomizerTests.java
@@ -63,6 +63,7 @@ class NettyReactiveWebServerFactoryCustomizerTests {
 	private NettyReactiveWebServerFactoryCustomizer customizer;
 
 	@Captor
+	@SuppressWarnings("NullAway.Init")
 	private ArgumentCaptor<NettyServerCustomizer> customizerCaptor;
 
 	@BeforeEach
@@ -196,6 +197,7 @@ class NettyReactiveWebServerFactoryCustomizerTests {
 		NettyServerCustomizer serverCustomizer = this.customizerCaptor.getAllValues().get(0);
 		HttpServer httpServer = serverCustomizer.apply(HttpServer.create());
 		Http2SettingsSpec decoder = httpServer.configuration().http2SettingsSpec();
+		assertThat(decoder).isNotNull();
 		assertThat(decoder.maxHeaderListSize()).isEqualTo(expected);
 	}