Provisioning datasource env variable

I have added in the grafana.ini:
GF_HISTORY_URL = http://172.24.68.44:8081/api/history/grafana

In my datasource (provisioned) I have:
url: $GF_SERVER_ROOT_URL

All works will when my docker-compose up --build,
but in the GUI the url is : GF_HISTORY_URL and not http://172.24.68.44:8081/api/history/grafana

Please help.