Restful problem: sending arguments containing slash (/)

Suppose I want to send an argument containing a slash (/) to a restful service, I am doing this with the following piece of code:

var _url = 'http://localhost:8080/servoy-service/rest_ws/my_services/my_services_form/my_service/argument1=' + encodeURIComponent('blabla/blabla')
var _res = plugins.http.getPageData(_url)

Variable _url will have the following value:

"http://localhost:8080/servoy-service/rest_ws/my_services/my_services_form/my_service/argument1=blabla%2fblabla"

But the ws_read method is not even triggered (if I leave out the slash, the method is triggered). Is this a bug or is it not possible to send an argument containing a slash (or maybe other special characters) in this way. I’m using Servoy 5.2.16.