Problem with starting of Workflow Service

While trying to implement some test I moved my WorkflowService (the Workflow hosted as Wcf service) from original project to some other one.
After that I could have noticed following error: 

                                          "No contract found in the workflow".

This error occurs if the workflow implementation is contained in the project which is not of the Workflow Project Type (no any of {SequentialWorkflowServiceLibrary,  StateMachineWorkflowServiceLibrary, SequentionalWorkflwoLibrary or StateMachineWorkflowLibrary}).

However, in my case I'm using the the workflow service, which naturally should also not be consisting part of the Workflow Project type. Instead such workflows (or services) have a special project type named "WorkflowService" (SequentialWorkflowServiceLibrary and StateMachineWorkflowServiceLibrary).
Note that one WorkflowService can be consisted in the project of common workflow type like SequentionalWorkflwoLibrary and StateMachineWorkflowLibrary.