diff --git a/src/Custom/Assistants/MessageContent.cs b/src/Custom/Assistants/MessageContent.cs
index d020a5c30..dab575342 100644
--- a/src/Custom/Assistants/MessageContent.cs
+++ b/src/Custom/Assistants/MessageContent.cs
@@ -19,7 +19,7 @@ public static MessageContent FromImageFileId(
             => new InternalMessageContentImageFileObject(
                 imageFile: new(
                     fileId: imageFileId,
-                    detail: detail?.ToString(),
+                    detail: detail?.ToSerialString(),
                     additionalBinaryDataProperties: null));
 
     /// <summary>
@@ -33,7 +33,7 @@ public static MessageContent FromImageUri(Uri imageUri, MessageImageDetail? deta
         => new InternalMessageContentImageUrlObject(
             imageUrl: new(
                 url: imageUri,
-                detail: detail?.ToString(),
+                detail: detail?.ToSerialString(),
                 additionalBinaryDataProperties: null));
 
     /// <summary>
diff --git a/tests/Assistants/AssistantsTests.cs b/tests/Assistants/AssistantsTests.cs
index 969055fb9..02cccae22 100644
--- a/tests/Assistants/AssistantsTests.cs
+++ b/tests/Assistants/AssistantsTests.cs
@@ -301,6 +301,45 @@ public async Task ThreadWithInitialMessagesWorks()
         Assert.That(messages[1].Content[1].ImageUri.AbsoluteUri, Is.EqualTo("https://test.openai.com/image.png"));
     }
 
+    [Test]
+    public async Task ThreadWithImageDetailWorks()
+    {
+        AssistantClient client = GetTestClient();
+
+        ThreadCreationOptions options = new()
+        {
+            InitialMessages =
+        {
+            new(
+                MessageRole.User,
+                [
+                    "Describe this image with auto detail:",
+                    MessageContent.FromImageUri(
+                        new Uri("https://test.openai.com/image.png"),
+                        MessageImageDetail.Auto)
+                ])
+        }
+        };
+
+        AssistantThread thread = IsAsync
+            ? await client.CreateThreadAsync(options)
+            : client.CreateThread(options);
+
+        Validate(thread);
+
+        MessageCollectionOptions collectionOptions = new() { Order = MessageCollectionOrder.Ascending };
+        List<ThreadMessage> messages = IsAsync
+            ? await client.GetMessagesAsync(thread.Id, collectionOptions).ToListAsync()
+            : client.GetMessages(thread.Id, collectionOptions).ToList();
+
+        Assert.That(messages.Count, Is.EqualTo(1));
+        Assert.That(messages[0].Role, Is.EqualTo(MessageRole.User));
+        Assert.That(messages[0].Content?.Count, Is.EqualTo(2));
+
+        Assert.That(messages[0].Content[0].Text, Is.EqualTo("Describe this image with auto detail:"));
+        Assert.That(messages[0].Content[1].ImageUri.AbsoluteUri, Is.EqualTo("https://test.openai.com/image.png"));
+    }
+
     [Test]
     public async Task BasicRunOperationsWork()
     {