diff --git a/CHANGELOG.md b/CHANGELOG.md
index c19d631..7aac346 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,13 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ## [Unreleased]
 
+## [v3.1064.0] - 2026-10-23
+
+### Changed
+- Updated `openapi`
+- Updated `v3-smile-links`
+
+
 ## [v3.1057.0] - 2026-10-22
 
 ### Changed
diff --git a/specs/v3/openapi.yaml b/specs/v3/openapi.yaml
index b7c840e..4c8a846 100644
--- a/specs/v3/openapi.yaml
+++ b/specs/v3/openapi.yaml
@@ -3462,7 +3462,7 @@ paths:
                 callback_url:
                   type: string
                   description: >-
-                    Defaults to the partner's configured callback when omitted. Otherwise a public HTTPS URL; private, loopback, link-local and internal addresses are rejected.
+                    Defaults to the partner's configured callback when omitted; if there is none, the request is rejected with 400. Otherwise a public HTTPS URL; private, loopback, link-local and internal addresses are rejected.
                 description:
                   type: string
                 expires_at:
diff --git a/specs/v3/v3-smile-links.yaml b/specs/v3/v3-smile-links.yaml
index f43013d..7e09c18 100644
--- a/specs/v3/v3-smile-links.yaml
+++ b/specs/v3/v3-smile-links.yaml
@@ -358,7 +358,7 @@ paths:
                   type: boolean
                 callback_url:
                   type: string
-                  description: Defaults to the partner's configured callback when omitted. Otherwise a public HTTPS URL; private, loopback, link-local and internal addresses are rejected.
+                  description: Defaults to the partner's configured callback when omitted; if there is none, the request is rejected with 400. Otherwise a public HTTPS URL; private, loopback, link-local and internal addresses are rejected.
                 description:
                   type: string
                 expires_at: