diff --git a/spring-test/src/main/java/org/springframework/test/web/reactive/server/DefaultControllerSpec.java b/spring-test/src/main/java/org/springframework/test/web/reactive/server/DefaultControllerSpec.java
index d1f41c2b087..9823a3adcce 100644
--- a/spring-test/src/main/java/org/springframework/test/web/reactive/server/DefaultControllerSpec.java
+++ b/spring-test/src/main/java/org/springframework/test/web/reactive/server/DefaultControllerSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -56,16 +56,21 @@ class DefaultControllerSpec extends AbstractMockServerSpec<WebTestClient.Control
 
 	DefaultControllerSpec(Object... controllers) {
 		Assert.isTrue(!ObjectUtils.isEmpty(controllers), "At least one controller is required");
+		Assert.isTrue(checkInstances(controllers), "Controller instances are required");
 		this.controllers = Arrays.asList(controllers);
 	}
 
-
 	@Override
 	public DefaultControllerSpec controllerAdvice(Object... controllerAdvice) {
+		Assert.isTrue(checkInstances(controllerAdvice), "ControllerAdvice instances are required");
 		this.controllerAdvice.addAll(Arrays.asList(controllerAdvice));
 		return this;
 	}
 
+	private boolean checkInstances(Object[] objects) {
+		return Arrays.stream(objects).noneMatch(Class.class::isInstance);
+	}
+
 	@Override
 	public DefaultControllerSpec contentTypeResolver(Consumer<RequestedContentTypeResolverBuilder> consumer) {
 		this.configurer.contentTypeResolverConsumer = consumer;
diff --git a/spring-test/src/main/java/org/springframework/test/web/servlet/setup/StandaloneMockMvcBuilder.java b/spring-test/src/main/java/org/springframework/test/web/servlet/setup/StandaloneMockMvcBuilder.java
index 622af32aced..34916ce0b95 100644
--- a/spring-test/src/main/java/org/springframework/test/web/servlet/setup/StandaloneMockMvcBuilder.java
+++ b/spring-test/src/main/java/org/springframework/test/web/servlet/setup/StandaloneMockMvcBuilder.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -143,6 +143,7 @@ public class StandaloneMockMvcBuilder extends AbstractMockMvcBuilder<StandaloneM
 	 */
 	protected StandaloneMockMvcBuilder(Object... controllers) {
 		Assert.isTrue(!ObjectUtils.isEmpty(controllers), "At least one controller is required");
+		Assert.isTrue(checkInstances(controllers), "Controller instances are required");
 		this.controllers = Arrays.asList(controllers);
 	}
 
@@ -157,10 +158,15 @@ public class StandaloneMockMvcBuilder extends AbstractMockMvcBuilder<StandaloneM
 	 * @since 4.2
 	 */
 	public StandaloneMockMvcBuilder setControllerAdvice(Object... controllerAdvice) {
+		Assert.isTrue(checkInstances(controllerAdvice), "ControllerAdvice instances are required");
 		this.controllerAdvice = Arrays.asList(controllerAdvice);
 		return this;
 	}
 
+	private boolean checkInstances(Object[] objects) {
+		return Arrays.stream(objects).noneMatch(Class.class::isInstance);
+	}
+
 	/**
 	 * Set the message converters to use in argument resolvers and in return value
 	 * handlers, which support reading and/or writing to the body of the request
diff --git a/spring-test/src/test/java/org/springframework/test/web/reactive/server/DefaultControllerSpecTests.java b/spring-test/src/test/java/org/springframework/test/web/reactive/server/DefaultControllerSpecTests.java
index 60d2748cc49..08e3598137e 100644
--- a/spring-test/src/test/java/org/springframework/test/web/reactive/server/DefaultControllerSpecTests.java
+++ b/spring-test/src/test/java/org/springframework/test/web/reactive/server/DefaultControllerSpecTests.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -44,7 +44,7 @@ import static org.junit.Assert.assertNotNull;
 public class DefaultControllerSpecTests {
 
 	@Test
-	public void controller() throws Exception {
+	public void controller() {
 		new DefaultControllerSpec(new MyController()).build()
 				.get().uri("/")
 				.exchange()
@@ -53,7 +53,7 @@ public class DefaultControllerSpecTests {
 	}
 
 	@Test
-	public void controllerAdvice() throws Exception {
+	public void controllerAdvice() {
 		new DefaultControllerSpec(new MyController())
 				.controllerAdvice(new MyControllerAdvice())
 				.build()
@@ -63,8 +63,18 @@ public class DefaultControllerSpecTests {
 				.expectBody(String.class).isEqualTo("Handled exception");
 	}
 
+	@Test(expected = IllegalArgumentException.class)
+	public void controllerIsAnObjectInstance() {
+		new DefaultControllerSpec(MyController.class);
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void controllerAdviceIsAnObjectInstance() {
+		new DefaultControllerSpec(new MyController()).controllerAdvice(MyControllerAdvice.class);
+	}
+
 	@Test
-	public void configurerConsumers() throws Exception {
+	public void configurerConsumers() {
 
 		TestConsumer<ArgumentResolverConfigurer> argumentResolverConsumer = new TestConsumer<>();
 		TestConsumer<RequestedContentTypeResolverBuilder> contenTypeResolverConsumer = new TestConsumer<>();
diff --git a/spring-test/src/test/java/org/springframework/test/web/servlet/setup/StandaloneMockMvcBuilderTests.java b/spring-test/src/test/java/org/springframework/test/web/servlet/setup/StandaloneMockMvcBuilderTests.java
index d8146dc7d22..651e595ff6f 100644
--- a/spring-test/src/test/java/org/springframework/test/web/servlet/setup/StandaloneMockMvcBuilderTests.java
+++ b/spring-test/src/test/java/org/springframework/test/web/servlet/setup/StandaloneMockMvcBuilderTests.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -125,6 +125,17 @@ public class StandaloneMockMvcBuilderTests {
 		assertNotNull(serializer);
 	}
 
+	@Test(expected = IllegalArgumentException.class)
+	public void controllerIsAnObjectInstance() {
+		new StandaloneMockMvcBuilder(PersonController.class);
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void controllerAdviceIsAnObjectInstance() {
+		new StandaloneMockMvcBuilder(new PersonController()).setControllerAdvice(PersonController.class);
+	}
+
+
 
 	@Controller
 	private static class PlaceholderController {