Airflow - Invalid JSON configuration, must be a dict

Airflow version: 2.1.1

I'm trying to trigger the dag using config and passing below json

{"load_type":"full"}

but it throws an error saying "Invalid JSON configuration, must be a dict"

I tried to format the json as well with 3spaces, 2 spaces etc

{
   "load_type":"full"
}

But it didn't work. Before this verison I was using 2.0.2 and I was able to send json while triggering the dag.

Any help would be appreciated. Thanks