How to keep the order of enumeration when updating a property with REST API

I have been able to use the REST API to update attributes in work items. So far this method is working fine

<url-of-workitem>?x-oslc-cm-change-request%2Bjson&oslc_cm.properties=rtc_cm:Fixed_Versions_EL
and I pass a json object { "Fixed_Versions_EL": [ "1.0", "1.1", "1.2"] }

This is working for all attributes, but I do have an issue with a field that is of type Enumeration List. In that case the order that I commit is not the one I see in the work item. For example the above request  will show up as 1.1 , 1.0, 1.2 which is correct but not what I expected..

Is there a way to prevent this, how can I keep the order. ( our server is running 5.0.2 ifix012 )