Conditional resolver in plugins sbt

I'm trying to exclude our snapshot repositories for the release build in sbt.

Therefore I thought of a environment variable or system property to control the stage I'm in, since I want to use ivy range syntax (e.g. '[1.0.0,)' ) for released versions of our own libraries and don't want to include SNAPSHOT versions of these libs. This does not compile:

resolvers += {
  val res : Seq[sbt.Resolver] = stage match {
    case "dev" => Seq("Our Artifactory snapshots2" at "https://bla/artifactory/snapshots/")
    case "release" => None
  }
  res
}

Is it possible to have conditionally added resolvers in sbt? Any advice would be appreciated. Thanks.

EDIT: I came to a solution, which is not very nice... I just add the releases a second time in the 'release' case:

resolvers += {
  val res : Seq[sbt.Resolver] = stage match {
    case "dev" => Seq("Our Artifactory snapshots2" at "https://bla/artifactory/snapshots/")
    case "release" => Seq("Our Artifactory release" at "https://bla/artifactory/releases/")
  }
  res
}

// here the releases repository is already added...
resolvers += "Our Artifactory release" at "https://bla/artifactory/releases/"