IntelliJ IDEA debug jumps inside instead of going over

I use last stable SBT with Scala 2.10 and last Scala plugin in IntelliJ IDEA 12.x. And have very simple test Scala project. I have specs2 test where I want to start my debug from. Having several breakpoints, I'm expecting going over lines, (from one break point to another - in my test and in My code), but instead: the debbuger going somewhere inside library classes, stops there, showing me some strange sources. That's reproducible all the time, and I have to click 2, 3, sometimes 5 times on the next-arrow-button (on debug panel) to reach next break point (in the test or in the code). I run my test with SBT 'test-compile' action, like IntelliJ pop-up suggests. Aldo I found this debug settings for Scala ("Do not step into specific Scala classes"). But I have this check-box selected. I've post an issue in IntelliJ IDEA site.