Can't resolve casbah as a sbt dependency

I'm getting the following error upon compile:

[error] (*:update) sbt.ResolveException: unresolved dependency: org.mongodb#casbah_2.11;2.7.4-SNAPSHOT: not found

With this build.sbt file:

name := """play-scala"""version := "1.0-SNAPSHOT"lazy val root = (project in file(".")).enablePlugins(PlayScala)scalaVersion := "2.11.1"libraryDependencies ++= Seq(  jdbc,  anorm,  cache,  ws)libraryDependencies += "org.mongodb" %% "casbah" % "2.7.4-SNAPSHOT"// For stable releasesresolvers += "Sonatype releases" at "https://oss.sonatype.org/content/repositories/releases"// For SNAPSHOT releasesresolvers += "Sonatype snapshots" at "https://oss.sonatype.org/content/repositories/snapshots"

I'm using Typesafe Activator and have tried many combinations of Casbah versions (including releases, instead of snapshots) and resolvers. The installation instructions from the "official" MongoDB Casbah tutorial don't work either. Any ideas?