nsubstitute received called with specific object argument

I have a class that looks something like this:

public myArguments
{
    public List<string> argNames {get; set;}
}

In my test I'm doing this:

var expectedArgNames = new List<string>();
expectedArgNames.Add("test");

_mockedClass.CheckArgs(Arg.Any<myArguments>()).Returns(1);

_realClass.CheckArgs();

_mockedClass.Received().CheckArgs(Arg.Is<myArguments>(x => x.Equals(expectedArgNames));

But the test fails with this error message:

NSubstitute.Exceptions.ReceivedCallsException : Expected to receive a call matching:
    CheckArgs(Foo[])
Actually received no matching calls.
Received 1 non-matching call (non-matching arguments indicated with '*' characters):
    CheckArgs(*myArguments*)

I'm guessing it's because of the .Equals() but I'm not sure how to solve it?