diff --git a/docs/content/docs/api/reference/contacts.mdx b/docs/content/docs/api/reference/contacts.mdx
index 9deb52e6..c9033cb6 100644
--- a/docs/content/docs/api/reference/contacts.mdx
+++ b/docs/content/docs/api/reference/contacts.mdx
@@ -673,7 +673,7 @@ Auth: **Scope** `READ_CONTACTS` · **Org permission** `view_contacts`
 | `id` | path | UUID | Contact ID. |
 | `limit` | query | integer | Page size, 1 to 200 (default 50). Anything else is a `400`. |
 | `cursor` | query | string | Opaque pagination cursor from `pagination.next_cursor`. A malformed cursor is a `400`. |
-| `before` | query | string (RFC 3339 nano) | Deprecated. Returns the events strictly older than this timestamp, which can skip events that share an instant with the page boundary; use `cursor`. Ignored when `cursor` is set. |
+| `before` | query | string (RFC 3339 nano) | Deprecated. Returns the events strictly older than this timestamp, which can skip events that share an instant with the page boundary; use `cursor`. A value that is not an RFC 3339 timestamp is a `400`. Ignored when `cursor` is set. |
 
 ### Response
 
diff --git a/docs/public/openapi.json b/docs/public/openapi.json
index 75fc754f..60c55cca 100644
--- a/docs/public/openapi.json
+++ b/docs/public/openapi.json
@@ -6854,7 +6854,7 @@
             }
           },
           "400": {
-            "description": "Invalid contact ID, limit or cursor, or no organization selected.",
+            "description": "Invalid contact ID, limit, cursor or before timestamp, or no organization selected.",
             "content": {
               "application/json": {
                 "schema": {