BigQuery StreamLoader on Container-Optimized OS Engine

Hi,
I was trying to get the new BigQuery StreamLoader 0.6.1 running on a container-optimized OS engine.

My script to do this is:
gcloud compute instances create-with-container bq-loader-instance \
--container-image snowplow-docker-registry.bintray.io/snowplow/snowplow-bigquery-streamloader:0.6.1 \
--container-arg="--config $(cat bigquery_config.json | base64 -w 0)" \
--container-arg="--resolver $(cat iglu_resolver.json | base64 -w 0)"

Getting the image works fine, but running it fails by:
Unexpected option: --config ...

The encoded iglu_resolver.json looks like: 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

Any idea what causes this problem? I am new to working with docker, so probably there is a fairly straight-forward solution.

Thanks!