# Field value equal "Unknown" get error
**URL:** https://discuss.elastic.co/t/field-value-equal-unknown-get-error/139692
**Category:** Elasticsearch
**Created:** [July 12, 2018, 7:51am UTC](https://discuss.elastic.co/t/field-value-equal-unknown-get-error/139692 "2018-07-12T07:51:04Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@Izek](https://discuss.elastic.co/u/Izek)
#### Post date: [July 12, 2018, 7:51am UTC](https://discuss.elastic.co/t/field-value-equal-unknown-get-error/139692/1 "2018-07-12T07:51:04Z")
I get the error message as below:
"error"=\>{"type"=\>"mapper\_parsing\_exception", "reason"=\>"failed to parse [details-RequestData-MessageTag]", "caused\_by"=\>{"type"=\>"illegal\_argument\_exception", "reason"=\>"For input string: "Unknown""}}
And in my json
```json
{"details-RequestData-MessageTag":"Unknown"}
```
Is it a bug or some rules that not allow to use "Unknown"?
---
### Author:  [@dadoonet](https://discuss.elastic.co/u/dadoonet)
#### Post date: [July 12, 2018, 8:14am UTC](https://discuss.elastic.co/t/field-value-equal-unknown-get-error/139692/2 "2018-07-12T08:14:02Z")
What exactly are you doing?
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### Author:  [@Izek](https://discuss.elastic.co/u/Izek)
#### Post date: [July 12, 2018, 8:58am UTC](https://discuss.elastic.co/t/field-value-equal-unknown-get-error/139692/3 "2018-07-12T08:58:46Z")
I am sending data to logstash.
But I got this error when it write to elasticsearch
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### Author:  [@dadoonet](https://discuss.elastic.co/u/dadoonet)
#### Post date: [July 12, 2018, 1:25pm UTC](https://discuss.elastic.co/t/field-value-equal-unknown-get-error/139692/4 "2018-07-12T13:25:46Z")
Ok but I still have no idea on what exactly you are doing.
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### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [August 9, 2018, 1:25pm UTC](https://discuss.elastic.co/t/field-value-equal-unknown-get-error/139692/5 "2018-08-09T13:25:54Z")
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