eb: error: unrecognized arguments: --database.engine.version

According to the AWS EB documentation for eb create, I should be able to create an elastic beanstalk environment with an postgres database, via this command:

eb create myapp --database.engine.version postgres-9.4.1                                                                                        
usage: eb {cmd} <environment_name> [options ...]
eb: error: unrecognized arguments: --database.engine.version postgres-9.4.1

I've also tried these command line arguments to no avail:

 eb create myapp -db.engine postgres --database.engine.version 9.4.1 

Any help is appreciated!