Mock Server.HtmlEncode - Returns Null Reference?

I'm trying to mock Server.HtmlEncode(), but I keep having a null reference exception.I'm pretty new to the Moq framework, here is my code:

var context = new Mock<HttpContextBase>();
var request = new Mock<HttpRequestBase>();
var response = new Mock<HttpResponseBase>();
var session = new Mock<HttpSessionStateBase>();
var server = new Mock<HttpServerUtilityBase>();
server.Setup(svr => svr.HtmlEncode(It.IsAny<string>())).Returns((string s) => s);
context.Setup(ctx => ctx.Request).Returns(request.Object);
context.Setup(ctx => ctx.Response).Returns(response.Object);
context.Setup(ctx => ctx.Session).Returns(session.Object);
context.Setup(ctx => ctx.Server).Returns(server.Object);

I've also tried the following:

context.Setup(ctx => ctx.Server.HtmlEncode(It.IsAny<string>())).Returns((string s) => s);

I've found a solution but it seems an outdated solution as expect is replaced with setup.