**Steps to replicate the issue** (include links if applicable):
* Use the Wikibase REST API to call a PUT request on Property:P570 of Robert Nixon Q7348050
Based on the issue reported here: https://www.wikidata.org/wiki/Wikidata:Project_chat#Need_help_regarding_a_PUT_request
**What happens?**:
* The API returns a 404 statement not found
**What should have happened instead?**:
* The proposed change in statement should have been successful
**Software version** (skip for WMF-hosted wikis like Wikipedia):
* REST API beta version on Wikidata
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**Acceptance criteria:***
REST API can handle statements with lowercase IDs but continue to display them with uppercase