should and thrownBy of org.scalatest.Matchers trait are not resolved

Hi,

I'm trying to build my tests using ScalaTest.
Although I can compile and run the tests, as you can see in the screenshot, should and thrownBy are marked with red telling "Cannot resolve symbol".

The code is just a copy/paste from http://www.scalatest.org/quick_start
So I guess it's configuration releated or a bug?

Thanks.
Selim

PS: Using Intellij 13 Build 133.162 with Scala Plugin 0.26.315