class Foo: def Do(param as object): debug param def Do[of T](param as T): debug param def test(): self.Do[of string]('asdf') f = Foo() f.Do[of string]('asdf') f.test() In the above code if I remove the reference to self, ie: I replace... self.Do[of string]('asdf') with... Do[of string]('asdf') The compiler fails with ... Entering Boo.Lang.Compiler.Steps.EmitAssembly ASSEMBLY LOADED: <dynamic>test2, Version=1.0.2974.0, Culture=neutral, PublicKeyToken=null ASSEMBLY LOADED: C:\WINDOWS\assembly\GAC_32\ISymWrapper\2.0.0.0__b03f5f7f11d50a3a\ISymWrapper.dll MyClass.boo(14,22): Internal compiler error on node 'Do[of string]('asdf')': System.NullReferenceException: Object reference not set to an instance of an object. at Boo.Lang.Compiler.Steps.EmitAssembly.InvokeRegularMethod(IMethod method, MethodInfo mi, MethodInvocationExpression node) at Boo.Lang.Compiler.Steps.EmitAssembly.InvokeMethod(IMethod method, MethodInvocationExpression node) at Boo.Lang.Compiler.Steps.EmitAssembly.OnMethodInvocationExpression(MethodInvocationExpression node) at Boo.Lang.Compiler.Ast.MethodInvocationExpression.Accept(IAstVisitor visitor) at Boo.Lang.Compiler.Ast.DepthFirstVisitor.Visit(Node node) Leaving Boo.Lang.Compiler.Steps.EmitAssembly