# Unknown filed type is not mapped

**URL:** <https://discuss.elastic.co/t/unknown-filed-type-is-not-mapped/85667>\
**Category:** Kibana\
**Created:** [May 14, 2017, 6:42am UTC](https://discuss.elastic.co/t/unknown-filed-type-is-not-mapped/85667 "2017-05-14T06:42:05Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![Christian\_Dahlqvist](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/christian_dahlqvist/32/4617_2.png) [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)\
**Post date:** [May 14, 2017, 9:39am UTC](https://discuss.elastic.co/t/unknown-filed-type-is-not-mapped/85667/2 "2017-05-14T09:39:20Z")

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I believe fields starting with an underscore are treated as reserved fields and [should not be allowed](https://discuss.elastic.co/t/illegal-characters-in-elasticsearch-field-names/17196). How did you manage to index a field that starts with an underscore? Which version of Elasticsearch are you on?

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