diff --git a/CHANGELOG.md b/CHANGELOG.md
index 55b25f7..a6e8aef 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,11 +4,10 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
-## [0.4.0] - 2024-07-??
-
-### Added
-- TODO
+## [0.3.1] - 2024-07-12
 
+### Changed
+- Upgraded Java SDK version to 8.9.2
 
 ## [0.3.0] - 2024-07-08
 
diff --git a/pom.xml b/pom.xml
index 26df024..e191b27 100644
--- a/pom.xml
+++ b/pom.xml
@@ -5,7 +5,7 @@
 
   <groupId>com.vonage</groupId>
   <artifactId>server-sdk-kotlin</artifactId>
-  <version>0.4.0</version>
+  <version>0.3.1</version>
 
   <packaging>jar</packaging>
   <name>Vonage Kotlin Server SDK</name>
@@ -53,13 +53,13 @@
   <dependencies>
     <dependency>
       <groupId>org.jetbrains.kotlin</groupId>
-      <artifactId>kotlin-stdlib-jdk8</artifactId>
+      <artifactId>kotlin-stdlib</artifactId>
       <version>2.0.0</version>
     </dependency>
     <dependency>
       <groupId>com.vonage</groupId>
       <artifactId>server-sdk</artifactId>
-      <version>8.9.1</version>
+      <version>8.9.2</version>
     </dependency>
     <dependency>
       <groupId>org.jetbrains.kotlin</groupId>
diff --git a/src/main/kotlin/com/vonage/client/kt/Conversion.kt b/src/main/kotlin/com/vonage/client/kt/Conversion.kt
index 4be1be8..42c9dbf 100644
--- a/src/main/kotlin/com/vonage/client/kt/Conversion.kt
+++ b/src/main/kotlin/com/vonage/client/kt/Conversion.kt
@@ -6,12 +6,14 @@ import java.util.*
 
 class Conversion(private val conversionClient: ConversionClient) {
 
-    private fun convert(type: ConversionRequest.Type, messageId: String, delivered: Boolean, timestamp: Instant) =
-        conversionClient.submitConversion(type, messageId, delivered, Date.from(timestamp))
+    private fun convert(type: ConversionRequest.Type, messageId: String, delivered: Boolean, timestamp: Instant?) =
+        conversionClient.submitConversion(type, messageId, delivered,
+            if (timestamp != null) Date.from(timestamp) else null
+        )
 
-    fun convertSms(messageId: String, delivered: Boolean, timestamp: Instant = Instant.now()) =
+    fun convertSms(messageId: String, delivered: Boolean, timestamp: Instant? = null) =
         convert(ConversionRequest.Type.SMS, messageId, delivered, timestamp)
 
-    fun convertVoice(callId: String, delivered: Boolean, timestamp: Instant = Instant.now()) =
+    fun convertVoice(callId: String, delivered: Boolean, timestamp: Instant? = null) =
         convert(ConversionRequest.Type.VOICE, callId, delivered, timestamp)
 }
diff --git a/src/test/kotlin/com/vonage/client/kt/AbstractTest.kt b/src/test/kotlin/com/vonage/client/kt/AbstractTest.kt
index 33b6ffd..dcfb9a4 100644
--- a/src/test/kotlin/com/vonage/client/kt/AbstractTest.kt
+++ b/src/test/kotlin/com/vonage/client/kt/AbstractTest.kt
@@ -141,7 +141,7 @@ abstract class AbstractTest {
                     val authHeaderName = "Authorization"
                     when (authType) {
                         AuthType.JWT -> headers contains authHeaderName like
-                                "Bearer eyJ0eXBlIjoiSldUIiwiYWxnIjoiUlMyNTYifQ(\\..+){2}"
+                                "Bearer eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9(\\..+){2}"
 
                         AuthType.API_KEY_SECRET_HEADER ->
                             headers contains authHeaderName equalTo "Basic $apiKeySecretEncoded"