Json.Net - adapt dictionary key serialization for single property

Question

I'm using a DefaultcontractResolver with CamelCaseNamingStrategy to serialize my dictionaries. For reasons outside my control, I temporarily have to serialize a single dictionary to PascalCase. Yet, I can't seem to get it to work.

I set up my serializer as follows

        var defaultSerializerSettings = new JsonSerializerSettings
        {
            ReferenceLoopHandling = ReferenceLoopHandling.Ignore,
            NullValueHandling = NullValueHandling.Ignore,
            Converters = new List<JsonConverter> { new Newtonsoft.Json.Converters.StringEnumConverter(new CamelCaseNamingStrategy()) },
        };
        defaultSerializerSettings.ContractResolver = new DefaultContractResolver
        {
            NamingStrategy = new CamelCaseNamingStrategy
            {
                OverrideSpecifiedNames = true,
                ProcessDictionaryKeys = true
            }
        };

My test class has two dictionaries, one that is supposed to be serialized per default, so camelCase with dictionary keys, and then one where it's supposed to be camelCase but leaving dictionary keys alone

    internal class TestClass
    {
        [JsonProperty(NamingStrategyType = typeof(CamelCaseNamingStrategy), NamingStrategyParameters = new object[] { true, false })]
        public Dictionary<string, string> CSVImportFileFieldMapping { get; set; }

        public Dictionary<string, string> CSVImportFileFieldMapping2 { get; set; }
    }

And then I create a testobject and serialize it

    var pb = new TestClass
    { 
        CSVImportFileFieldMapping = new Dictionary<string, string> { { "Hello", "World" }, { "Gaga", "Gugu" } },
        CSVImportFileFieldMapping2 = new Dictionary<string, string> { { "Hello", "World" }, { "Gaga", "Gugu" } },
    };
    var jsonString = JsonConvert.SerializeObject(pb, defaultSerializerSettings);

Yet, both dictionaries have their keys pascalCased.

Any idea what I'm missing here?