WebAPI returns corrupted, incomplete file

I want to return an image from WebApi endpoint. This is my method:

[System.Web.Http.HttpGet]
public HttpResponseMessage GetAttachment(string id)
{
    string dirPath = HttpContext.Current.Server.MapPath(Constants.ATTACHMENT_FOLDER);
    string path = string.Format($"{dirPath}\\{id}.jpg");

    try
    {
        HttpResponseMessage result = new HttpResponseMessage(HttpStatusCode.OK);
        var stream = new FileStream(path, FileMode.Open, FileAccess.Read);

        var content = new StreamContent(stream);
        result.Content = content;
        result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
        result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment") { FileName = Path.GetFileName(path) };
        return result;
    }
    catch (FileNotFoundException ex)
    {
        _log.Warn($"Image {path} was not found on the server.");
        return Request.CreateResponse(HttpStatusCode.NotFound, "Invalid image ID");
    }
}

Unfortunately, the file that is downloaded is incomplete. The message in consuming Android app is:

java.io.EOFException: source exhausted prematurely