A binary operator with incompatible types was detected. Found operand types 'Edm.Guid' and 'Edm.String' for operator type 'equals'

I get the following exception when calling OData from Kendo ListView:

"Binary operators with incompatible types detected. Operand types 'Edm.Guid' and 'Edm.String' found for operator type 'Equal'"

Decoded filter:
$filter=OrganizationId eq'4c2c1c1e-1838-42ca-b730-399816de85f8'

Encoded filter:
%24filter=OrganizationId+eq+%274c2c1c1e-1838-42ca-b730-399816de85f8%27

Haven't tried these filters successfully yet:
$ filter = OrganizationId eq guid '4c2c1c1e-1838-42ca-b730-399816de85f8'
$ filter = OrganizationId eq cast('4c2c1c1e-1838-42ca-b730-399816de85f8', Edm.

My Web API call looks like this:

// GET: odata/Sites
[HttpGet]
[EnableQuery]
public IHttpActionResult GetSites(ODataQueryOptions<Site> queryOptions)
{
    IQueryable<Site> sites = null;

    try
    {
        queryOptions.Validate(_validationSettings);
        sites = _siteService.GetAll().OrderBy(x => x.SiteName);

        if (sites == null)
            return NotFound();
    }
    catch (ODataException ex)
    {
        TraceHandler.TraceError(ex);
        return BadRequest(ex.Message);
    }

    return Ok(sites);
}

My JAVASCRIPT KENDO datasource looks like:

var dataSource = new kendo.data.DataSource({

    filter: { field: "OrganizationId", operator: "eq", value: that.settings.current.customer.id },
    schema: {
        data: function (data) {
            return data.value;
        },
        total: function (data) {
            return data.length;
        }
    },
    serverFiltering: true,
    serverPaging: true,
    transport: {
        parameterMap: function (options, type) {

            var paramMap = kendo.data.transports.odata.parameterMap(options);

            // Remove invalid Parameters that Web API doesn't support
            delete paramMap.$inlinecount; // <-- remove inlinecount
            delete paramMap.$format; // <-- remove format
            delete paramMap.$callback; // <-- remove callback

            // PLEASE NOTICE: That I have tried reformatting unsuccessfully
            //paramMap.$filter = paramMap.$filter.replace("OrganizationId eq ", "OrganizationId eq guid");
            //paramMap.$filter = "OrganizationId eq cast('81de6144-987c-4b6f-a9bd-355cb6597fc1', Edm.Guid)";

            return paramMap;
        },
        read: {
            url: buildRoute('odata/Sites')
            , dataType: 'json'
        }
    },
    type: 'odata'
});