Cannot load any Portable Class Library projects in VS 2013 solution, when it is opened in VS2015 RC

While I am trying to load any Portable Class Library (Universal Windows 8.1 Project) I see an error "TargetPlatformIdentifier is not supported. One or more 'Windows' projects have <TargetPlatformIdentifier> not equal to 'Windows'.

Adding TargetPlatformIdentifier key don't help. Project looks as the default PCL project in VS2015 RC.