diff --git a/CHANGES.md b/CHANGES.md
index 1e929c0832..9b8dcc6472 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -8,6 +8,17 @@
 
 - Drop support for unstable field names from the long-accepted [MSC2732](https://github.com/matrix-org/matrix-spec-proposals/pull/2732) (Olm fallback keys) proposal. This change allows unit tests to pass following the security patch above. ([\#18996](https://github.com/element-hq/synapse/issues/18996))
 
+
+
+# Synapse 1.138.4 (2025-10-07)
+
+## Bugfixes
+
+- Fix a bug introduced in 1.138.3 where a client could receive an Internal Server Error if they set `device_keys: null` in the request to [`POST /_matrix/client/v3/keys/upload`](https://spec.matrix.org/v1.16/client-server-api/#post_matrixclientv3keysupload). ([\#19023](https://github.com/element-hq/synapse/issues/19023))
+
+
+
+
 # Synapse 1.138.3 (2025-10-07)
 
 ## Security Fixes
diff --git a/debian/changelog b/debian/changelog
index 7922f851ef..7a1d20ec5c 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -4,6 +4,12 @@ matrix-synapse-py3 (1.139.1) stable; urgency=medium
 
  -- Synapse Packaging team <packages@matrix.org>  Tue, 07 Oct 2025 11:46:51 +0100
 
+matrix-synapse-py3 (1.138.4) stable; urgency=medium
+
+  * New Synapse release 1.138.4.
+
+ -- Synapse Packaging team <packages@matrix.org>  Tue, 07 Oct 2025 16:28:38 +0100
+
 matrix-synapse-py3 (1.138.3) stable; urgency=medium
 
   * New Synapse release 1.138.3.