Configuration for lagom.persistence.read-side.jdbc.slick not resolving correctly

In one project, we have an application in our tests where the values for lagom.persistence.read-side.jdbc.slick are resolving to the default values (H2 profile) as configured by testkit, even though we have the following in our application.conf:

db.default.driver = "org.postgresql.Driver"
jdbc-defaults.slick.profile = "slick.jdbc.PostgresProfile$"

When I check the application configuration on startup, it is reading that correctly from application.conf, however, when I inspect lagom.persistence.read-side.jdbc.slick.driver and lagom.persistence.read-side.jdbc.slick.profile they contain the default settings from the testkit reference.conf (and so it tries to use H2 and fails). The lagom-persistence-jdbc-core has a reference.conf that should be resolving those values from the application.conf:

  # Slick configuration
  slick {

    # The Slick profile
    profile = ${?jdbc-defaults.slick.profile}

    # The Slick driver - for backward compatibility only, will be removed in 1.5.0 (@deprecated)
    driver = ${?jdbc-defaults.slick.driver}

    jndiDbName = ${jdbc-defaults.slick.jndiDbName}
  }

What would cause the configuration to resolve out of order?

For now I’m just hard-coding those values in our application.conf and that resolves the issue:

lagom.persistence.read-side.jdbc.slick.driver = "org.postgresql.Driver"
lagom.persistence.read-side.jdbc.slick.profile = "slick.jdbc.PostgresProfile$"

PS this is where it’s getting the H2 defaults from lagom/reference.conf at master · lagom/lagom · GitHub