Play 2.3 RjsKeys.mainModule causes Error: paths fallback not supported in optimizer

Question

On build.sbt, if I use these configs for rjs,

 RjsKeys.mainConfig := "build",
 RjsKeys.mainModule := "mainAccount",
 RjsKeys.modules += WebJs.JS.Object("name" -> "mainSFCanvas")

it gives me this error: [info] Error: Error: paths fallback not supported in optimizer. Please provide a build config path override for angular

I have to make 'build' as mainModule to solve the above warning. Is this correct workaround?

RjsKeys.mainConfig := "build",
RjsKeys.mainModule := "build",
RjsKeys.modules := Seq(
        WebJs.JS.Object("name" -> "mainAccount"),
        WebJs.JS.Object("name" -> "mainSFCanvas")
    )