creation of stem cell fails because openstack api_key is not an instance of String

Hi,

I am trying to deploy cloud foundry on openstack using travelling bosh. After the stemcell gets uploaded, it fails at

create stemcell failed: Invalid OpenStack cloud properties: #<Membrane::SchemaValidationError: { openstack => { api_key => Expected instance of String, given an instance of Fixnum } }>:

Neither changing the openstack password nor editing the api_key in micro_bosh.yml helps. Does anybody have any ideas?