Eclipse. Perfoce. Error in change specification. Can't include file(s) not already opened. Error in change specification. Can't include file(s) not already opened.

Recently I faced the problem using P4-Eclipse integration. The message said like the one specified in this post's subject. So, googling gave nothing but only the that lot of people face the same kind of problem but actually of different reasons. Now after the short investigation I can share my one.
It seems eclipse gets mad if the current client spec is set up with some client view different from looking straight into the storage root. You should either to remap client view or to use another client spec.