Can't store term_vector

[Kornelia_Watson]

Hi all,

If I understand documentation correctly (v 5.1 term_vector | Elasticsearch Guide [5.1] | Elastic)

I should be able to set term_vector by doing "term_vector": "yes". But when I do so I get:

[mapper_parsing_exception] Mapping definition for [entities] has unsupported parameters: [term_vector : yes]

What am I doing wrong?
Example:

.....
"elements": {
"type": "nested",
"term_vector": "yes",
"properties": {
"id": {
"type": "keyword"
} ...
}
}