Custom content object not appearing in Content Manager due to case sensitivity

Why is my custom_dto content not appearing in Beamable Content Manager? I have a file named CustomDTO.cs with these contents:

using Beamable.Common.Content;

[ContentType("custom_dto")]
public class CustomDto : ContentObject
{
	public int likes;
	public string topic;
}

But when I look in Content Manager, there is no content type entry for custom_dto. Other content types I have defined show up just fine. Why is this?