diff --git a/spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/catalog/BeanFactoryAwareFunctionRegistry.java b/spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/catalog/BeanFactoryAwareFunctionRegistry.java
index 842adbcf1..9c7e63860 100644
--- a/spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/catalog/BeanFactoryAwareFunctionRegistry.java
+++ b/spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/catalog/BeanFactoryAwareFunctionRegistry.java
@@ -164,10 +164,6 @@ public class BeanFactoryAwareFunctionRegistry
 		return this.registrationsByFunction.get(function);
 	}
 
-	public FunctionType getFunctionType(String name) {
-		return FunctionType.of(FunctionTypeUtils.getFunctionType(this.lookup(name), this));
-	}
-
 	private Object locateFunction(String name) {
 		Object function = null;
 		if (this.applicationContext.containsBean(name)) {
@@ -214,6 +210,7 @@ public class BeanFactoryAwareFunctionRegistry
 					.filter(n -> !n.endsWith(FunctionRegistration.REGISTRATION_NAME_SUFFIX) && !n.equals(RoutingFunction.FUNCTION_NAME)).toArray(String[]::new);
 			String[] supplierNames  = Stream.of(this.applicationContext.getBeanNamesForType(Supplier.class))
 					.filter(n -> !n.endsWith(FunctionRegistration.REGISTRATION_NAME_SUFFIX) && !n.equals(RoutingFunction.FUNCTION_NAME)).toArray(String[]::new);
+
 			/*
 			 * we may need to add BiFunction and BiConsumer at some point
 			 */
@@ -221,7 +218,8 @@ public class BeanFactoryAwareFunctionRegistry
 					.concat(Stream.of(functionNames), Stream.concat(Stream.of(consumerNames), Stream.of(supplierNames))).collect(Collectors.toList());
 
 			if (!ObjectUtils.isEmpty(names)) {
-				Assert.isTrue(names.size() == 1, "Found more then one function in BeanFactory: " + names);
+				Assert.isTrue(names.size() == 1, "Found more then one function in BeanFactory: " + names
+						+ ". Consider providing 'spring.cloud.function.definition' property.");
 				definition = names.get(0);
 			}
 			else {
@@ -230,6 +228,15 @@ public class BeanFactoryAwareFunctionRegistry
 					definition = this.registrationsByName.keySet().iterator().next();
 				}
 			}
+
+			if (StringUtils.hasText(definition)) {
+				Type functionType = discoverFunctionType(this.applicationContext.getBean(definition), definition);
+				if (!FunctionTypeUtils.isSupplier(functionType) && !FunctionTypeUtils.isFunction(functionType) && !FunctionTypeUtils.isConsumer(functionType)) {
+					logger.info("Discovered functional instance of bean '" + definition + "' as a default function, however its "
+							+ "function argument types can not be determined. Discarding.");
+					definition = null;
+				}
+			}
 		}
 		return definition;
 	}
@@ -576,8 +583,11 @@ public class BeanFactoryAwareFunctionRegistry
 				List<MimeType> acceptedContentTypes = MimeTypeUtils.parseMimeTypes(acceptedOutputMimeTypes[0].toString());
 
 				convertedValue = acceptedContentTypes.stream()
-						.map(acceptedContentType -> messageConverter
-								.toMessage(value, new MessageHeaders(Collections.singletonMap(MessageHeaders.CONTENT_TYPE, acceptedContentType))))
+						.map(acceptedContentType -> {
+							Object v = value instanceof Message ? ((Message<?>) value).getPayload() : value;
+							return messageConverter
+								.toMessage(v, new MessageHeaders(Collections.singletonMap(MessageHeaders.CONTENT_TYPE, acceptedContentType)));
+							})
 						.filter(v -> v != null)
 						.findFirst().orElse(null);
 			}
diff --git a/spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/catalog/FunctionTypeUtils.java b/spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/catalog/FunctionTypeUtils.java
index ac09be1ca..f7a942019 100644
--- a/spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/catalog/FunctionTypeUtils.java
+++ b/spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/catalog/FunctionTypeUtils.java
@@ -128,14 +128,6 @@ public final class FunctionTypeUtils {
 		}
 	}
 
-	public static Type getFunctionType(Object function, FunctionInspector inspector) {
-		FunctionRegistration<?> registration = inspector.getRegistration(function);
-		if (registration != null) {
-			return registration.getType().getType();
-		}
-		return null;
-	}
-
 	public static Type unwrapActualTypeByIndex(Type type, int index) {
 		if (isMessage(type) || isPublisher(type)) {
 			if (isPublisher(type)) {
diff --git a/spring-cloud-function-context/src/test/java/org/springframework/cloud/function/context/catalog/BeanFactoryAwareFunctionRegistryTests.java b/spring-cloud-function-context/src/test/java/org/springframework/cloud/function/context/catalog/BeanFactoryAwareFunctionRegistryTests.java
index ed3033880..55a064f9e 100644
--- a/spring-cloud-function-context/src/test/java/org/springframework/cloud/function/context/catalog/BeanFactoryAwareFunctionRegistryTests.java
+++ b/spring-cloud-function-context/src/test/java/org/springframework/cloud/function/context/catalog/BeanFactoryAwareFunctionRegistryTests.java
@@ -17,6 +17,7 @@
 package org.springframework.cloud.function.context.catalog;
 
 
+import java.io.Serializable;
 import java.nio.charset.StandardCharsets;
 import java.util.List;
 import java.util.Map;
@@ -53,7 +54,11 @@ import static org.assertj.core.api.Assertions.assertThat;
 public class BeanFactoryAwareFunctionRegistryTests {
 
 	private FunctionCatalog configureCatalog() {
-		ApplicationContext context = new SpringApplicationBuilder(SampleFunctionConfiguration.class)
+		return this.configureCatalog(SampleFunctionConfiguration.class);
+	}
+
+	private FunctionCatalog configureCatalog(Class<?>... configClass) {
+		ApplicationContext context = new SpringApplicationBuilder(configClass)
 				.run("--logging.level.org.springframework.cloud.function=DEBUG",
 						"--spring.main.lazy-initialization=true");
 		FunctionCatalog catalog = context.getBean(FunctionCatalog.class);
@@ -268,6 +273,15 @@ public class BeanFactoryAwareFunctionRegistryTests {
 		result.getT3().subscribe(v -> System.out.println("=> 3: " + v));
 	}
 
+	@Test
+	public void SCF_GH_409ConfigurationTests() {
+		FunctionCatalog catalog = this.configureCatalog(SCF_GH_409ConfigurationAsSupplier.class);
+		assertThat((Object) catalog.lookup("")).isNull();
+
+		catalog = this.configureCatalog(SCF_GH_409ConfigurationAsFunction.class);
+		assertThat((Object) catalog.lookup("")).isNull();
+	}
+
 
 	@EnableAutoConfiguration
 	@Configuration
@@ -431,6 +445,46 @@ public class BeanFactoryAwareFunctionRegistryTests {
 		}
 	}
 
+	@EnableAutoConfiguration
+	public static class SCF_GH_409ConfigurationAsSupplier {
+
+		@Bean
+		public Serializable blah() {
+			return new Foo();
+		}
+
+		private static class Foo implements Supplier<Object>, Serializable {
+
+			@Override
+			public Object get() {
+				// TODO Auto-generated method stub
+				return null;
+			}
+
+		}
+	}
+
+	@EnableAutoConfiguration
+	public static class SCF_GH_409ConfigurationAsFunction {
+
+		@Bean
+		public Serializable blah() {
+			return new Foo();
+		}
+
+		private static class Foo implements Function<Object, Object>, Serializable {
+
+			@Override
+			public Object apply(Object t) {
+				// TODO Auto-generated method stub
+				return null;
+			}
+
+
+
+		}
+	}
+
 	public static class Person {
 		private String name;
 		private int id;