Error while trying to export survey responses using API

Hi Gurus,
I am getting the below error message, while trying to export survey responses using the API.

InboundJaxrsResponse{context=ClientResponse{method=POST, uri=https://xxxx.qualtrics.com/API/v3/surveys/SV_0djWsLPMe1Zfhf7/export-responses, status=411, reason=Length Required}}

I am trying the below API call to export the responses, and to see the Export Request ID.

curl -X POST -H 'X-API-TOKEN: yourapitokenhere' -H 'Content-Type: application/json' -d '{
"format": "csv"
}' 'https://yourdatacenterid.qualtrics.com/API/v3/surveys/SV_012345678912345/export-responses'

Any help is greatly appreciated.

Thanks
Sri