(where the hell did the Interpreter component for JIRA go?) As noted by yury on IRC, there appears to be a bug when instanizing value types inside of booish. Here's a cleaned up example. import System.Drawing p = Point() ####RESULTS#### System.InvalidCastException: Unable to cast object of type 'System.Drawing.Point ' to type 'System.IConvertible'. at Boo.Lang.Runtime.RuntimeServices.CheckNumericPromotion(Object value) at Boo.Lang.Runtime.RuntimeServices.UnboxBoolean(Object value) at Boo.Lang.Runtime.RuntimeServices.ToBool(Object value) at Boo.Lang.Interpreter.InteractiveInterpreter.ProcessLastValue() at Boo.Lang.Interpreter.InteractiveInterpreter.InternalLoopEval(String code) at Boo.Lang.Interpreter.InteractiveInterpreter.ConsoleLoopEval()