Implicits session is not found in passed anonymous function

gistfile1.scala

package models

import org.specs2.mutable.Specification
import play.api.Play.current
import play.api.db.slick.{DB, Session}
import play.api.db.slick.Config.driver.simple._
import play.api.test.FakeApplication
import play.api.test.Helpers._

class UserSpec extends Specification {

  "UserRepository" should {
    "save new user" in {
      withDatabase {
          val user = User("Octocat", "[email protected]")
          val savedUser = Users.save(user)
          val foundUser = Users.find(savedUser.id.get).get
          foundUser.name must beEqualTo("Octocat")
          foundUser.email must beEqualTo("[email protected]")
      }
    }
  }

  def withDatabase[T](test: => T): T =
    running(FakeApplication(additionalConfiguration = inMemoryDatabase())) {
      DB.withSession { implicit session: Session =>
        test
      }
    }
}

If I wrap test directly in DB.withSession, e.g.

"save new user" in {
  running(FakeApplication(additionalConfiguration = inMemoryDatabase())) {
    DB.withSession { implicit session: Session =>
      val user = User("Octocat", "[email protected]")
      val savedUser = Users.save(user)
      val foundUser = Users.find(savedUser.id.get).get
      foundUser.name must beEqualTo("Octocat")
      foundUser.email must beEqualTo("[email protected]")
    }
  }
}

Spec file is compiled without any problems.