diff --git a/spring-boot-project/spring-boot-docs/src/main/kotlin/org/springframework/boot/docs/data/nosql/couchbase/repositories/MyConverter.kt b/spring-boot-project/spring-boot-docs/src/main/kotlin/org/springframework/boot/docs/data/nosql/couchbase/repositories/MyConverter.kt
index f6714bb2bc1..1d06d2f77fa 100644
--- a/spring-boot-project/spring-boot-docs/src/main/kotlin/org/springframework/boot/docs/data/nosql/couchbase/repositories/MyConverter.kt
+++ b/spring-boot-project/spring-boot-docs/src/main/kotlin/org/springframework/boot/docs/data/nosql/couchbase/repositories/MyConverter.kt
@@ -18,9 +18,9 @@ package org.springframework.boot.docs.data.nosql.couchbase.repositories
 
 import org.springframework.core.convert.converter.Converter
 
-internal class MyConverter : Converter<CouchbaseProperties?, Boolean> {
+internal class MyConverter : Converter<CouchbaseProperties, Boolean> {
 
-	override fun convert(value: CouchbaseProperties?): Boolean {
+	override fun convert(value: CouchbaseProperties): Boolean {
 		return true
 	}
 
diff --git a/spring-boot-project/spring-boot-docs/src/main/kotlin/org/springframework/boot/docs/messaging/amqp/receiving/custom/MyMessageConverter.kt b/spring-boot-project/spring-boot-docs/src/main/kotlin/org/springframework/boot/docs/messaging/amqp/receiving/custom/MyMessageConverter.kt
index f76819aea35..43223184d1a 100644
--- a/spring-boot-project/spring-boot-docs/src/main/kotlin/org/springframework/boot/docs/messaging/amqp/receiving/custom/MyMessageConverter.kt
+++ b/spring-boot-project/spring-boot-docs/src/main/kotlin/org/springframework/boot/docs/messaging/amqp/receiving/custom/MyMessageConverter.kt
@@ -22,12 +22,12 @@ import org.springframework.amqp.support.converter.MessageConverter
 
 internal class MyMessageConverter : MessageConverter {
 
-	override fun toMessage(`object`: Any, messageProperties: MessageProperties): Message? {
-		return null
+	override fun toMessage(`object`: Any, messageProperties: MessageProperties): Message {
+		return Message(byteArrayOf())
 	}
 
-	override fun fromMessage(message: Message): Any? {
-		return null
+	override fun fromMessage(message: Message): Any {
+		return Any()
 	}
 
 }
diff --git a/spring-boot-project/spring-boot-docs/src/main/kotlin/org/springframework/boot/docs/messaging/jms/receiving/custom/MyMessageConverter.kt b/spring-boot-project/spring-boot-docs/src/main/kotlin/org/springframework/boot/docs/messaging/jms/receiving/custom/MyMessageConverter.kt
index 2e5205d579b..a6210a47856 100644
--- a/spring-boot-project/spring-boot-docs/src/main/kotlin/org/springframework/boot/docs/messaging/jms/receiving/custom/MyMessageConverter.kt
+++ b/spring-boot-project/spring-boot-docs/src/main/kotlin/org/springframework/boot/docs/messaging/jms/receiving/custom/MyMessageConverter.kt
@@ -22,12 +22,12 @@ import org.springframework.jms.support.converter.MessageConverter
 
 internal class MyMessageConverter : MessageConverter {
 
-	override fun toMessage(`object`: Any, session: Session): Message? {
-		return null
+	override fun toMessage(`object`: Any, session: Session): Message {
+		return session.createObjectMessage()
 	}
 
-	override fun fromMessage(message: Message): Any? {
-		return null
+	override fun fromMessage(message: Message): Any {
+		return Any()
 	}
 
 }
diff --git a/spring-boot-project/spring-boot-docs/src/main/kotlin/org/springframework/boot/docs/web/servlet/springmvc/messageconverters/AdditionalHttpMessageConverter.kt b/spring-boot-project/spring-boot-docs/src/main/kotlin/org/springframework/boot/docs/web/servlet/springmvc/messageconverters/AdditionalHttpMessageConverter.kt
index f7c224f781c..d851f33d004 100644
--- a/spring-boot-project/spring-boot-docs/src/main/kotlin/org/springframework/boot/docs/web/servlet/springmvc/messageconverters/AdditionalHttpMessageConverter.kt
+++ b/spring-boot-project/spring-boot-docs/src/main/kotlin/org/springframework/boot/docs/web/servlet/springmvc/messageconverters/AdditionalHttpMessageConverter.kt
@@ -23,19 +23,19 @@ import org.springframework.http.converter.HttpMessageNotReadableException
 import org.springframework.http.converter.HttpMessageNotWritableException
 import java.io.IOException
 
-open class AdditionalHttpMessageConverter : AbstractHttpMessageConverter<Any?>() {
+open class AdditionalHttpMessageConverter : AbstractHttpMessageConverter<Any>() {
 
-	override fun supports(clazz: Class<*>?): Boolean {
+	override fun supports(clazz: Class<*>): Boolean {
 		return false
 	}
 
 	@Throws(IOException::class, HttpMessageNotReadableException::class)
-	override fun readInternal(clazz: Class<*>?, inputMessage: HttpInputMessage): Any? {
-		return null
+	override fun readInternal(clazz: Class<*>, inputMessage: HttpInputMessage): Any {
+		return Any()
 	}
 
 	@Throws(IOException::class, HttpMessageNotWritableException::class)
-	override fun writeInternal(t: Any?, outputMessage: HttpOutputMessage) {
+	override fun writeInternal(t: Any, outputMessage: HttpOutputMessage) {
 	}
 
 }