diff --git a/spring-boot-project/spring-boot-tools/spring-boot-test-support/src/main/java/org/springframework/boot/testsupport/classpath/resources/ResourcesClassLoader.java b/spring-boot-project/spring-boot-tools/spring-boot-test-support/src/main/java/org/springframework/boot/testsupport/classpath/resources/ResourcesClassLoader.java
index 2eeef880c1..eab1f7ad65 100644
--- a/spring-boot-project/spring-boot-tools/spring-boot-test-support/src/main/java/org/springframework/boot/testsupport/classpath/resources/ResourcesClassLoader.java
+++ b/spring-boot-project/spring-boot-tools/spring-boot-test-support/src/main/java/org/springframework/boot/testsupport/classpath/resources/ResourcesClassLoader.java
@@ -19,16 +19,19 @@ package org.springframework.boot.testsupport.classpath.resources;
 import java.io.IOException;
 import java.io.UncheckedIOException;
 import java.net.URL;
+import java.security.ProtectionDomain;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Enumeration;
 
+import org.springframework.core.SmartClassLoader;
+
 /**
  * A {@link ClassLoader} that provides access to {@link Resources resources}.
  *
  * @author Andy Wilkinson
  */
-class ResourcesClassLoader extends ClassLoader {
+class ResourcesClassLoader extends ClassLoader implements SmartClassLoader {
 
 	private final Resources resources;
 
@@ -66,4 +69,14 @@ class ResourcesClassLoader extends ClassLoader {
 		return Collections.enumeration(urls);
 	}
 
+	@Override
+	public ClassLoader getOriginalClassLoader() {
+		return getParent();
+	}
+
+	@Override
+	public Class<?> publicDefineClass(String name, byte[] b, ProtectionDomain protectionDomain) {
+		return defineClass(name, b, 0, b.length, protectionDomain);
+	}
+
 }