Complete suggestion ignore spaces

[mlkmhd (Benjamin)]

when I'm using Completion Suggester, it ignores spaces. for example if I search foo b the result isn't contains foo bar but when I search for fo the result contains foo bar

this is my index mapping:

     {
        "mappings": {
          "tag": {
            "properties": {
              "suggest": {
                "type": "completion",
                "analyzer": "simple",
                "preserve_separators": true,
                "preserve_position_increments": true,
                "max_input_length": 50
              }
            }
          }
        }
    }

my request:

POST http://localhost:9200/index/_search
    {
      "suggest": {
        "tag_suggests": {
          "prefix": "foo f",
          "completion": {
            "field": "suggest"
          }
        }
      }
    }

and the result not contains foo bar. but when I search for foo the result contails foo bar !