diff --git a/spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/message/MessageUtils.java b/spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/message/MessageUtils.java
index 64c9c975a..f8f9cde9e 100644
--- a/spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/message/MessageUtils.java
+++ b/spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/message/MessageUtils.java
@@ -90,10 +90,12 @@ public abstract class MessageUtils {
 			return MessageBuilder.withPayload(message).build();
 		}
 		ClassLoader classLoader = ((Isolated) handler).getClassLoader();
-		Class<?> type = ClassUtils.resolveClassName(Message.class.getName(), classLoader);
+		Class<?> type = ClassUtils.isPresent(Message.class.getName(), classLoader)
+				? ClassUtils.resolveClassName(Message.class.getName(), classLoader)
+				: null;
 		Object payload;
 		Map<String, Object> headers;
-		if (type.isAssignableFrom(message.getClass())) {
+		if (type != null && type.isAssignableFrom(message.getClass())) {
 			Method getPayload = ClassUtils.getMethod(type, "getPayload");
 			Method getHeaders = ClassUtils.getMethod(type, "getHeaders");
 			payload = ReflectionUtils.invokeMethod(getPayload, message);
@@ -101,7 +103,8 @@ public abstract class MessageUtils {
 			Map<String, Object> map = (Map<String, Object>) ReflectionUtils
 					.invokeMethod(getHeaders, message);
 			headers = map;
-		} else {
+		}
+		else {
 			payload = message;
 			headers = Collections.emptyMap();
 		}
diff --git a/spring-cloud-function-samples/function-sample-pojo/.attach_pid9535 b/spring-cloud-function-samples/function-sample-pojo/.attach_pid9535
deleted file mode 100644
index e69de29bb..000000000
diff --git a/spring-cloud-function-stream/src/test/java/org/springframework/cloud/function/stream/function/ClassLoaderUtils.java b/spring-cloud-function-stream/src/test/java/org/springframework/cloud/function/stream/function/ClassLoaderUtils.java
index 6ebbe69b9..c3b901e30 100644
--- a/spring-cloud-function-stream/src/test/java/org/springframework/cloud/function/stream/function/ClassLoaderUtils.java
+++ b/spring-cloud-function-stream/src/test/java/org/springframework/cloud/function/stream/function/ClassLoaderUtils.java
@@ -17,6 +17,7 @@
 package org.springframework.cloud.function.stream.function;
 
 import java.io.File;
+import java.net.MalformedURLException;
 import java.net.URL;
 import java.net.URLClassLoader;
 import java.util.ArrayList;
@@ -38,19 +39,40 @@ import reactor.core.publisher.Flux;
  *
  */
 public class ClassLoaderUtils {
-	
+
 	@Test
 	public void fluxIsShared() {
-		Class<?> flux = ClassUtils.resolveClassName(Flux.class.getName(), createClassLoader());
+		Class<?> flux = ClassUtils.resolveClassName(Flux.class.getName(),
+				createClassLoader());
 		assertThat(flux).isEqualTo(Flux.class);
 	}
 
 	@Test
 	public void messageIsNotShared() {
-		Class<?> flux = ClassUtils.resolveClassName(Message.class.getName(), createClassLoader());
+		Class<?> flux = ClassUtils.resolveClassName(Message.class.getName(),
+				createClassLoader());
 		assertThat(flux).isNotEqualTo(Message.class);
 	}
 
+	@Test(expected = IllegalArgumentException.class)
+	public void messageIsNotAvailable() {
+		Class<?> flux = ClassUtils.resolveClassName(Message.class.getName(),
+				createMinimalClassLoader());
+		assertThat(flux).isNotEqualTo(Message.class);
+	}
+
+	public static ClassLoader createMinimalClassLoader() {
+		ClassLoader base = ClassLoaderUtils.class.getClassLoader();
+		try {
+			return new URLClassLoader(
+					new URL[] { new File("target/test-classes").toURI().toURL() },
+					base.getParent());
+		}
+		catch (MalformedURLException e) {
+			throw new IllegalStateException(e);
+		}
+	}
+
 	public static ClassLoader createClassLoader() {
 		URL[] urls = findClassPath();
 		if (urls.length == 1) {
@@ -171,4 +193,5 @@ public class ClassLoaderUtils {
 			}
 		}
 	}
+
 }
diff --git a/spring-cloud-function-stream/src/test/java/org/springframework/cloud/function/stream/function/MessageUtilsTests.java b/spring-cloud-function-stream/src/test/java/org/springframework/cloud/function/stream/function/MessageUtilsTests.java
index bd537b4bc..e2efbab17 100644
--- a/spring-cloud-function-stream/src/test/java/org/springframework/cloud/function/stream/function/MessageUtilsTests.java
+++ b/spring-cloud-function-stream/src/test/java/org/springframework/cloud/function/stream/function/MessageUtilsTests.java
@@ -73,7 +73,18 @@ public class MessageUtilsTests {
 		Object output = MessageUtils.unpack(function, "foo");
 		assertThat(output).isInstanceOf(Message.class);
 		@SuppressWarnings("unchecked")
-		Message<String> message = (Message<String>)output;
+		Message<String> message = (Message<String>) output;
+		assertThat(message.getPayload()).isEqualTo("foo");
+	}
+
+	@Test
+	public void testUnpackIsolatedMessageNotAvailable() throws Exception {
+		Object function = create(Uppercase.class,
+				ClassLoaderUtils.createMinimalClassLoader());
+		Object output = MessageUtils.unpack(function, "foo");
+		assertThat(output).isInstanceOf(Message.class);
+		@SuppressWarnings("unchecked")
+		Message<String> message = (Message<String>) output;
 		assertThat(message.getPayload()).isEqualTo("foo");
 	}
 
@@ -89,6 +100,10 @@ public class MessageUtilsTests {
 	}
 
 	private Object create(Class<Uppercase> type) {
+		return create(type, loader);
+	}
+
+	private Object create(Class<Uppercase> type, ClassLoader loader) {
 		return new IsolatedFunction<>((Function<?, ?>) BeanUtils
 				.instantiate(ClassUtils.resolveClassName(type.getName(), loader)));
 	}