What steps will reproduce the problem? 1. Run the attached program 2. 3.

What is the expected output? What do you see instead? Throws an exception when using a mock'd implementation of a generic interface, ok when using a non-generic interface.

What version of the product are you using? On what operating system? Win7, Moq 4.2.1402.2112, .NET 4.5.1

Please provide any additional information below. Full Error: Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object. at Microsoft.CSharp.RuntimeBinder.ExpressionTreeCallRewriter.GenerateLambda(EXPRCALL pExpr) at Microsoft.CSharp.RuntimeBinder.ExpressionTreeCallRewriter.VisitCALL(EXPRCALL pExpr) at Microsoft.CSharp.RuntimeBinder.Semantics.ExprVisitorBase.Dispatch(EXPR pExpr) at Microsoft.CSharp.RuntimeBinder.Semantics.ExprVisitorBase.Visit(EXPR pExpr) at Microsoft.CSharp.RuntimeBinder.ExpressionTreeCallRewriter.Rewrite(TypeManager typeManager, EXPR pExpr, IEnumerable`1 listOfParameters)

at Microsoft.CSharp.RuntimeBinder.RuntimeBinder.CreateExpressionTreeFromResult(IEnumerable1 parameters, ArgumentObject[] arguments, Scop e pScope, EXPR pResult) at Microsoft.CSharp.RuntimeBinder.RuntimeBinder.BindCore(DynamicMetaObjectBinder payload, IEnumerable1 parameters, DynamicMetaObject[] a rgs, DynamicMetaObject& deferredBinding) at Microsoft.CSharp.RuntimeBinder.RuntimeBinder.Bind(DynamicMetaObjectBinder payload, IEnumerable1 parameters, DynamicMetaObject[] args, DynamicMetaObject& deferredBinding) at Microsoft.CSharp.RuntimeBinder.BinderHelper.Bind(DynamicMetaObjectBinder action, RuntimeBinder binder, IEnumerable1 args, IEnumerable 1 arginfos, DynamicMetaObject onBindingError) at Microsoft.CSharp.RuntimeBinder.CSharpConvertBinder.FallbackConvert(DynamicMetaObject target, DynamicMetaObject errorSuggestion) at System.Dynamic.DynamicMetaObject.BindConvert(ConvertBinder binder) at System.Dynamic.ConvertBinder.Bind(DynamicMetaObject target, DynamicMetaObject[] args) at System.Dynamic.DynamicMetaObjectBinder.Bind(Object[] args, ReadOnlyCollection1 parameters, LabelTarget returnLabel) at System.Runtime.CompilerServices.CallSiteBinder.BindCore[T](CallSite1 site, Object[] args) at System.Dynamic.UpdateDelegates.UpdateAndExecute1[T0,TRet](CallSite site, T0 arg0) at TestDynamic.Program.GenericDoStuffDynamic[T](IInterface1 obj, T input) in c:\TFS\TestProjects\TestDynamic\TestDynamic\Program.cs:line 37 at TestDynamic.Program.Main(String[] args) in c:\TFS\TestProjects\TestDynamic\TestDynamic\Program.cs:line 27

The exception only seems to happen when the generic type parameter is object. I've tested with value types (Guid, int) and custom reference type they all work.