CloudKit web services bad request when uploading asset

The steps to set asset values using Cloudkit Web services are:

1. Request URLs for uploading asset data.
2. Upload the asset data.
3. Set the asset fields in records to the uploaded data.

I am getting the URL from step 1.

Then I am supposed to upload my asset using the given url ($[ASSET_UPLOAD_URL])

The Cloudkit reference document gives a curl command as an example:

curl -X POST $[ASSET_UPLOAD_URL] -d@[ASSET_FILE]

The problem is that when I am using this command in the Terminal, I have a "bad request" as a response.

But If I use the same command without the asset file, it kind of succeed with the following answer:

{"singleFile":{"size":0,"fileChecksum":"AW2cWT2PxzWixMKuuNMTHJ8CJ3sH"}}

Has anyone manage to send assets using the Cloudkit web services ?