"System.ServiceModel requires Business edition", but System.ServiceModel is not referenced.

Hi. I have a solution consisting of

1. a portable class library (.NET4.5 + WP8 + Windows store apps), Profile78
2. an Android application that references the portable library.

Neither project references System.ServiceModel.dll! But when I try to build the solution, Xamarin Studio stops with error message:

Error XA9003: Assembly 'System.ServiceModel, Version=2.0.5.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' requiresВ BusinessВ (or higher) License. (XA9003) (Application)

What can I do about it? My software versions:

• Xamarin Studio Version 4.0.13 (build 38),
• Xamarin.Android Version: 4.8.3 (Indie Edition)