diff --git a/spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/context/FilteredClassLoader.java b/spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/context/FilteredClassLoader.java
index 903da876d7..5d6a8236c3 100644
--- a/spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/context/FilteredClassLoader.java
+++ b/spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/context/FilteredClassLoader.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -20,12 +20,14 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.net.URL;
 import java.net.URLClassLoader;
+import java.security.ProtectionDomain;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Enumeration;
 import java.util.function.Predicate;
 
+import org.springframework.core.SmartClassLoader;
 import org.springframework.core.io.ClassPathResource;
 
 /**
@@ -37,7 +39,7 @@ import org.springframework.core.io.ClassPathResource;
  * @author Roy Jacobs
  * @since 2.0.0
  */
-public class FilteredClassLoader extends URLClassLoader {
+public class FilteredClassLoader extends URLClassLoader implements SmartClassLoader {
 
 	private final Collection<Predicate<String>> classesFilters;
 
@@ -129,6 +131,16 @@ public class FilteredClassLoader extends URLClassLoader {
 		return super.getResourceAsStream(name);
 	}
 
+	@Override
+	public Class<?> publicDefineClass(String name, byte[] b, ProtectionDomain protectionDomain) {
+		for (Predicate<String> filter : this.classesFilters) {
+			if (filter.test(name)) {
+				throw new IllegalArgumentException(String.format("Defining class with name %s is not supported", name));
+			}
+		}
+		return defineClass(name, b, 0, b.length, protectionDomain);
+	}
+
 	/**
 	 * Filter to restrict the classes that can be loaded.
 	 */
diff --git a/spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/context/FilteredClassLoaderTests.java b/spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/context/FilteredClassLoaderTests.java
index e184652899..a488d433e4 100644
--- a/spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/context/FilteredClassLoaderTests.java
+++ b/spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/context/FilteredClassLoaderTests.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -26,6 +26,7 @@ import org.springframework.core.io.ClassPathResource;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
+import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 
 /**
  * Tests for {@link FilteredClassLoader}.
@@ -111,4 +112,13 @@ class FilteredClassLoaderTests {
 		}
 	}
 
+	@Test
+	void publicDefineClassWhenFilteredThrowsException() throws Exception {
+		Class<FilteredClassLoaderTests> hiddenClass = FilteredClassLoaderTests.class;
+		try (FilteredClassLoader classLoader = new FilteredClassLoader(hiddenClass)) {
+			assertThatIllegalArgumentException()
+					.isThrownBy(() -> classLoader.publicDefineClass(hiddenClass.getName(), new byte[] {}, null));
+		}
+	}
+
 }
diff --git a/spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/context/runner/AbstractApplicationContextRunnerTests.java b/spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/context/runner/AbstractApplicationContextRunnerTests.java
index 4a12319aa6..ced8d3d6ee 100644
--- a/spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/context/runner/AbstractApplicationContextRunnerTests.java
+++ b/spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/context/runner/AbstractApplicationContextRunnerTests.java
@@ -25,6 +25,8 @@ import org.junit.jupiter.api.Test;
 
 import org.springframework.beans.factory.BeanDefinitionStoreException;
 import org.springframework.boot.context.annotation.UserConfigurations;
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.boot.test.context.FilteredClassLoader;
 import org.springframework.boot.test.context.assertj.ApplicationContextAssertProvider;
 import org.springframework.context.ConfigurableApplicationContext;
@@ -33,6 +35,7 @@ import org.springframework.context.annotation.Condition;
 import org.springframework.context.annotation.ConditionContext;
 import org.springframework.context.annotation.Conditional;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Lazy;
 import org.springframework.core.env.Environment;
 import org.springframework.core.type.AnnotatedTypeMetadata;
 import org.springframework.util.ClassUtils;
@@ -165,6 +168,15 @@ abstract class AbstractApplicationContextRunnerTests<T extends AbstractApplicati
 				.run((context) -> assertThat(context).hasSingleBean(ConditionalConfig.class));
 	}
 
+	@Test
+	void consecutiveRunWithFilteredClassLoaderShouldHaveBeanWithLazyProperties() {
+		get().withClassLoader(new FilteredClassLoader(Gson.class)).withUserConfiguration(LazyConfig.class)
+				.run((context) -> assertThat(context).hasSingleBean(ExampleBeanWithLazyProperties.class));
+
+		get().withClassLoader(new FilteredClassLoader(Gson.class)).withUserConfiguration(LazyConfig.class)
+				.run((context) -> assertThat(context).hasSingleBean(ExampleBeanWithLazyProperties.class));
+	}
+
 	@Test
 	void thrownRuleWorksWithCheckedException() {
 		get().run((context) -> assertThatIOException().isThrownBy(() -> throwCheckedException("Expected message"))
@@ -241,6 +253,30 @@ abstract class AbstractApplicationContextRunnerTests<T extends AbstractApplicati
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	@EnableConfigurationProperties(ExampleProperties.class)
+	static class LazyConfig {
+
+		@Bean
+		ExampleBeanWithLazyProperties exampleBeanWithLazyProperties() {
+			return new ExampleBeanWithLazyProperties();
+		}
+
+	}
+
+	static class ExampleBeanWithLazyProperties {
+
+		@Autowired
+		@Lazy
+		ExampleProperties exampleProperties;
+
+	}
+
+	@ConfigurationProperties
+	public static class ExampleProperties {
+
+	}
+
 	static class FilteredClassLoaderCondition implements Condition {
 
 		@Override