diff --git a/CHANGELOG.md b/CHANGELOG.md
index e1b40fb77..461bfd17a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 # [8.9.2] - 2024-07-12
 - Refactoring to accommodate using v2.0.0 of Vonage JWT library
+- Made `timestamp` optional in Conversion API
 - Fixed `SpeechSettings.Language.NEPALI` (de)serialisation
 - `fromRandomNumber` true if `from` is not specified in `Call.Builder`
 - Fixed `com.vonage.client.voice.EventWebhook` deserialisation issue
diff --git a/src/main/java/com/vonage/client/conversion/ConversionRequest.java b/src/main/java/com/vonage/client/conversion/ConversionRequest.java
index 79a6104d2..b0dbe9f63 100644
--- a/src/main/java/com/vonage/client/conversion/ConversionRequest.java
+++ b/src/main/java/com/vonage/client/conversion/ConversionRequest.java
@@ -21,6 +21,11 @@
 import java.util.LinkedHashMap;
 import java.util.Map;
 
+/**
+ *
+ * @deprecated This class will be made package-private in the next major release.
+ */
+@Deprecated
 public class ConversionRequest implements QueryParamsRequest {
     private final Type type;
     private final String messageId;
@@ -55,10 +60,15 @@ public Map<String, String> makeParams() {
         LinkedHashMap<String, String> params = new LinkedHashMap<>(4);
         params.put("message-id", messageId);
         params.put("delivered", String.valueOf(delivered));
-        params.put("timestamp", new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(timestamp));
+        if (timestamp != null) {
+            params.put("timestamp", new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(timestamp));
+        }
         return params;
     }
 
+    /**
+     * This enum will be moved to its own class in the next major release.
+     */
     public enum Type {
         SMS, VOICE
     }
diff --git a/src/test/java/com/vonage/client/conversion/ConversionClientTest.java b/src/test/java/com/vonage/client/conversion/ConversionClientTest.java
index 9444e3f53..de6c72e67 100644
--- a/src/test/java/com/vonage/client/conversion/ConversionClientTest.java
+++ b/src/test/java/com/vonage/client/conversion/ConversionClientTest.java
@@ -28,10 +28,7 @@
 import org.junit.jupiter.api.*;
 import java.text.ParseException;
 import java.text.SimpleDateFormat;
-import java.util.Arrays;
-import java.util.Collection;
-import java.util.LinkedHashMap;
-import java.util.Map;
+import java.util.*;
 
 public class ConversionClientTest extends AbstractClientTest<ConversionClient> {
 
@@ -40,21 +37,24 @@ public ConversionClientTest() {
     }
 
     @Test
-    public void testSuccessfulResponse() throws Exception {
+    public void testSuccessWithTimestamp() throws Exception {
         stubResponse(200);
-        client.submitConversion(ConversionRequest.Type.VOICE,
-                             "MESSAGE-ID",
-                             true,
-                             new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").parse("2014-03-04 10:11:12"));
+        client.submitConversion(ConversionRequest.Type.VOICE, UUID.randomUUID().toString(), false,
+                new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").parse("2014-03-04 10:11:12")
+        );
+    }
+
+    @Test
+    public void testSuccessWithoutTimestamp() throws Exception {
+        stubResponse(200);
+        client.submitConversion(ConversionRequest.Type.SMS, "MESSAGE-ID", true, null);
     }
 
     @Test
     public void testWrongCredentials() throws Exception {
         stubResponse(401);
         assertThrows(VonageApiResponseException.class, () -> client.submitConversion(
-                    ConversionRequest.Type.SMS,
-                     "MESSAGE-ID",
-                    true,
+                    ConversionRequest.Type.SMS, "MESSAGE-ID", true,
                      new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").parse("2014-03-04 10:11:12")
         ));
     }