FulfillSalesOrder action problem in javascript

Hi,

I'm trying to use FulfillSalesOrder action from javascript and getting an error:

{
"error":{
"code":"","message":"Resource not found for the segment 'FulfillSalesOrder'.","innererror":{
"message":"Resource not found for the segment 'FulfillSalesOrder'.","type":"Microsoft.OData.Core.UriParser.ODataUnrecognizedPathException","stacktrace":" at Microsoft.OData.Core.UriParser.Parsers.ODataPathParser.CreateFirstSegment(String segmentText)\r\n at Microsoft.OData.Core.UriParser.Parsers.ODataPathParser.ParsePath(ICollection`1 segments)\r\n at Microsoft.OData.Core.UriParser.Parsers.ODataPathFactory.BindPath(ICollection`1 segments, ODataUriParserConfiguration configuration)\r\n at Microsoft.OData.Core.UriParser.ODataUriParser.Initialize()\r\n at Microsoft.OData.Core.UriParser.ODataUriParser.ParsePath()\r\n at System.Web.OData.Routing.DefaultODataPathHandler.Parse(IEdmModel model, String serviceRoot, String odataPath, ODataUriResolverSetttings resolverSettings, Boolean enableUriTemplateParsing)\r\n at System.Web.OData.Routing.DefaultODataPathHandler.Parse(IEdmModel model, String serviceRoot, String odataPath)\r\n at Microsoft.Crm.Extensibility.OData.CrmODataPathHandler.Parse(IEdmModel model, String serviceRoot, String odataPath)"
}
}
}

Any idea what I'm doing wrong?

Here is the code I'm using:

var parameters = {};
var entityset1 = {};
entityset1.primarykeyid = myOrderid;
entityset1["@odata.type"] = "Microsoft.Dynamics.CRM.salesorder";
parameters.entityset = [entityset1];
var orderclose = {};
orderclose.primarykeyid = "00000000-0000-0000-0000-000000000000";
orderclose["@odata.type"] = "Microsoft.Dynamics.CRM.orderclose";
parameters.OrderClose = orderclose;
parameters.Status = 100001;

$.ajax({
type: "POST",
contentType: "application/json; charset=utf-8",
datatype: "json",
url: Xrm.Page.context.getClientUrl() + "/api/data/v8.2/FulfillSalesOrder",
data: JSON.stringify(parameters),
beforeSend: function(XMLHttpRequest) {
XMLHttpRequest.setRequestHeader("OData-MaxVersion", "4.0");
XMLHttpRequest.setRequestHeader("OData-Version", "4.0");
XMLHttpRequest.setRequestHeader("Accept", "application/json");
},
async: false,
success: function(data, textStatus, xhr) {
var results = data;
},
error: function(xhr, textStatus, errorThrown) {
Xrm.Utility.alertDialog(textStatus + " " + errorThrown);
}
});

Thanks in advance,

Laszlo