A class with an object property storing a Dictionary<string, string> doesn't deserialize properly

[ignusfast]

I have a simple class with an object property. If I store a Dictionary<string, string> in that property and serialize/deserialize the class, the Dictionary comes back as a Dictionary<string, object>. Because I'm expecting the former, my cast fails and nothing works. I assume this is because no types are being embedded for the Dictionary, but I need a way to override this, if possible.

I have a class that contains an object called Response.
public class DataCacheResponse {
public DataCacheResponse();

   public string LastError { get; set; }
   public object Response { get; set; }

}

In Response, I’m sending a Dictionary<string, string>.
When I serialize it as below, you can see the Dictionary values look correct, but there’s no type information at all.
{
"$types": { "MainAssembly.DataCacheResponse, MainAssembly, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b2997cac92e35e61": "1" },
"$type": "1",
"LastError": "",
"Response": {
"poo": "poop",
"pee": "peep"
}
}

Here’s the test code:
var rq3 = new DataCacheResponse() {
LastError = string.Empty,
Response = new Dictionary<string, string>() { { "poo", "poop" }, { "pee", "peep" } }
};
var js3 = rq3.ToTypedJson();
Console.WriteLine($"Json: {js3}");
var r23 = js3.FromTypedJson();
Console.WriteLine($"Object: {r23.LastError} - {((Dictionary<string, string>)r23.Response)["poo"]}");

So when I deserialize the above, the deserialization works, but the Dictionary<string, string> is actually being deserialized as a Dictionary<string, object>. So in that last line, when I try to cast it to Dictionary<string, string> it fails.
System.InvalidCastException
HResult=0x80004002
Message=Unable to cast object of type 'System.Collections.Generic.Dictionary2[System.String,System.Object]' to type 'System.Collections.Generic.Dictionary2[System.String,System.String]'.
Source=TestValidation

If I instead do this, it works, but this is far less than desirable…
Console.WriteLine($"Object: {r23.LastError} - {((Dictionary<string, object>)r23.Response)["poo"]}");