Firebase did not specify an index even when using .indexOn correctly

I tried to work with Firebase (2.2.5) API / .orderByChild ('score') operation and I keep getting

No index defined for score

      

        
        
        
      

    

Although the Firebase states documentation I do not need to create an index to evaluate when using the WebSocket API, I created one. Markup:

rules

{
"rules": {
    ".read": false,
    ".write": false,

    /* index players by score */
    "Players": {
      ".read": true,
      ".indexOn": "score",
      "$playerID": {
        ".write": "!data.exists() || data.child('uid').val() === auth.uid"
      }
    }
  }
}

      

        
        
        
      

    

Data

{
    "Players": {

      "-JpqOuoaHmcA2EngEvSZ" : {
        ".priority" : 0.0,
        "avatar" : "https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRS9Yh2lWzGP1oojIwNVV2JQUZYFX4_4pxvaADz8TfDF_WGrHbs",
        "draw" : 9,
        "lastTimeAccessed" : 1432705280027,
        "lost" : 7,
        "name" : "Hans",
        "score" : 126,
        "won" : 36
      },

      "-JpzVTpXZUZG-V0qJCDT" : {
        ".priority" : 2.0,
        "avatar" : "http://static.wixstatic.com/media/6a9a03_f979928a006c4d2ebc179c1c627dc119.png_srz_300_300_75_22_0.50_1.20_0.00_png_srz",
        "draw" : 0,
        "lastTimeAccessed" : 1432705280532,
        "lost" : 25,
        "name" : "Safari",
        "score" : 9,
        "won" : 3
      }
    }
}

      

        
        
        
      

    

Call

I have a Firebase () object pointed to by http://theapp.firebaseio.com/Players , on which I call orderByChild ('score'). I would have expected this to work.

We look forward to fresh views or tips.