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title: X
description: If you sent PATCH /v1/monitors/{id} with interval_seconds (the name a monitor is read with), the API answered 200 and quietly kept the old interval. That was…
canonical: https://watchfor.io/changelog/2026-09-30-api-patch-unknown-fields
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[All updates](/changelog/page/2#2026-09-30-api-patch-unknown-fields) 🐛 Fixed Sep 30, 2026 · v 9.0.9

# REST API: a monitor update with an unknown field is refused, not ignored

If you sent PATCH /v1/monitors/{id} with interval_seconds (the name a monitor is read with), the API answered 200 and quietly kept the old interval. That was our bug. An update now returns 400 naming every field it doesn't take and what to send instead, e.g. "interval" in seconds, and nothing is changed. Requests that only use the documented fields work as before.

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Canonical page: https://watchfor.io/changelog/2026-09-30-api-patch-unknown-fields · Site guide: https://watchfor.io/llms.txt