Unknown field , parser not found

[li_jessen2016 (Li Jessen)]

When I follow the instructions in the getting started with elasticsearch video on https://www.elastic.co/webinars/getting-started-elasticsearch. I found that:
"type": "x_content_parse_exception",
"reason": "[10:9] [field_sort] unknown field [coordinates], parser not found"

My query is:
GET /inspections/_doc/_search
{
"query":{
"match": {
"business_name": "Express"
}
},
"sort":[
{
"geo_distance": {
"coordinates":{
"lat": 37.800175,
"lon": -122.409081
},
"order": "asc",
"unit": "km",
"distance_type": "plane"
}
}
]

}
Why?

[li_jessen2016 (Li Jessen)]

Solved it. The error arose from a spelling mistake: geo_distance, with a surplus of a tailing _ , should be _geo_distance instead.