diff --git a/spring-cloud-function-context/pom.xml b/spring-cloud-function-context/pom.xml
index 3233746af..fb23fec49 100644
--- a/spring-cloud-function-context/pom.xml
+++ b/spring-cloud-function-context/pom.xml
@@ -120,7 +120,7 @@
 			<plugin>
 				<artifactId>kotlin-maven-plugin</artifactId>
 				<groupId>org.jetbrains.kotlin</groupId>
-				<version>1.4.21</version>
+				<version>1.6.0-RC</version>
 				<configuration>
 					<args>
 						<arg>-Xjsr305=strict</arg>
@@ -159,7 +159,7 @@
 					<dependency>
 						<groupId>org.jetbrains.kotlin</groupId>
 						<artifactId>kotlin-maven-allopen</artifactId>
-						<version>1.4.21</version>
+						<version>1.6.0-RC</version>
 					</dependency>
 				</dependencies>
 			</plugin>
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 58c298e93..91bd06857 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
@@ -880,9 +880,11 @@ public class BeanFactoryAwareFunctionRegistryTests {
 
 				@SuppressWarnings("unchecked")
 				@Override
-				protected Object doApply(Message<byte[]> input, FunctionInvocationWrapper targetFunction) {
-					MessageBuilder.fromMessage(input).setHeader("before", "foo").build();
-					Message<Object> result = (Message<Object>) targetFunction.apply(MessageBuilder.fromMessage(input).setHeader("before", "foo").build());
+				protected Object doApply(Object input, FunctionInvocationWrapper targetFunction) {
+					// in this test we know input is a Message
+					Message<?> mInput = (Message<?>) input;
+					MessageBuilder.fromMessage(mInput).setHeader("before", "foo").build();
+					Message<Object> result = (Message<Object>) targetFunction.apply(MessageBuilder.fromMessage(mInput).setHeader("before", "foo").build());
 					return MessageBuilder.fromMessage(result).setHeader("after", "bar").build();
 				}
 			};
diff --git a/spring-cloud-function-kotlin/pom.xml b/spring-cloud-function-kotlin/pom.xml
index b87165efb..d7c524263 100644
--- a/spring-cloud-function-kotlin/pom.xml
+++ b/spring-cloud-function-kotlin/pom.xml
@@ -64,7 +64,7 @@
 			<plugin>
 				<artifactId>kotlin-maven-plugin</artifactId>
 				<groupId>org.jetbrains.kotlin</groupId>
-				<version>1.4.21</version>
+				<version>1.6.0-RC</version>
 				<configuration>
 					<args>
 						<arg>-Xjsr305=strict</arg>
@@ -93,7 +93,7 @@
 					<dependency>
 						<groupId>org.jetbrains.kotlin</groupId>
 						<artifactId>kotlin-maven-allopen</artifactId>
-						<version>1.4.21</version>
+						<version>1.6.0-RC</version>
 					</dependency>
 				</dependencies>
 			</plugin>
diff --git a/spring-cloud-function-samples/function-sample-kotlin-web/pom.xml b/spring-cloud-function-samples/function-sample-kotlin-web/pom.xml
index a96818ab4..311a1cb6f 100644
--- a/spring-cloud-function-samples/function-sample-kotlin-web/pom.xml
+++ b/spring-cloud-function-samples/function-sample-kotlin-web/pom.xml
@@ -28,10 +28,12 @@
 		<dependency>
 			<groupId>org.jetbrains.kotlin</groupId>
 			<artifactId>kotlin-reflect</artifactId>
+			<version>1.6.0-RC</version>
 		</dependency>
 		<dependency>
 			<groupId>org.jetbrains.kotlin</groupId>
 			<artifactId>kotlin-stdlib-jdk8</artifactId>
+			<version>1.6.0-RC</version>
 		</dependency>
 		<dependency>
 			<groupId>org.springframework.cloud</groupId>
@@ -77,6 +79,7 @@
 			<plugin>
 				<groupId>org.jetbrains.kotlin</groupId>
 				<artifactId>kotlin-maven-plugin</artifactId>
+				<version>1.6.0-RC</version>
 				<configuration>
 					<args>
 						<arg>-Xjsr305=strict</arg>