Boo.Lang exception in my WP8.1 project

Here I met a new strange issue, it reported the error from Boo.Lang.DLL, but I've never used any *.boo. The code is about HashTable, so I guess it didn't find any hashtable classes, so use the existing one from Boo.Lang??

Exception: System.Boolean System.Type::IsInstanceOfType(System.Object) called in c:\buildslave\mono-runtime-and-classlibs\build\external\boo\src\Boo.Lang\Runtime\RuntimeServices.cs (243, 4).
Type: System.MissingMemberException
Module: Boo.Lang
InnerException: <No Data>...

Boo.Lang exception in my WP8.1 project