Why does sbt override scala version in sub project?

[Андрей Спиридонов]

Hi! I have failed to find any answers about  how to control scala version in sub project. Below is my case: 

lazy val sevone = Project(id = "sevone",      
    base = file("sevone")) dependsOn nmsCommons

 

  lazy val nmsCommons = Project(id = "nms-commons",
    base = file("nms-commons"))

where sevone project has 2.11.0 scala version and  nmsCommons has 2.10.2

When I'm trying to compile sevone sbt overrides scala version in subproject from 2.10.2 to 2.11.0 and sbt fails with 

Stack trace suppressed: run 'last sevone/*:update' for the full output.
[error] (sevone/*:update) sbt.ResolveException: unresolved dependency: network-monitoring-system-commons#network-monitoring-system-commons_2.11;1.0: not found

How can I tell to sbt not to override version? Maybe crossScalaVersions or something? I've tried but all just the same(