diff --git a/CHANGES.md b/CHANGES.md
index 066f798a95..13239e3504 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,3 +1,12 @@
+Synapse 1.38.1 (2021-07-22)
+===========================
+
+Bugfixes
+--------
+
+- Always include `device_one_time_keys_count` key in `/sync` response to work around a bug in Element Android that broke encryption for new devices. ([\#10457](https://github.com/matrix-org/synapse/issues/10457))
+
+
 Synapse 1.39.0rc1 (2021-07-20)
 ==============================
 
diff --git a/debian/changelog b/debian/changelog
index 55f7ee003c..ce8e2105e7 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -4,6 +4,12 @@ matrix-synapse-py3 (1.39.0ubuntu1) UNRELEASED; urgency=medium
 
  -- Richard van der Hoff <richard@matrix.org>  Tue, 20 Jul 2021 00:10:03 +0100
 
+matrix-synapse-py3 (1.38.1) stable; urgency=medium
+
+  * New synapse release 1.38.1.
+
+ -- Synapse Packaging team <packages@matrix.org>  Thu, 22 Jul 2021 15:37:06 +0100
+
 matrix-synapse-py3 (1.39.0~rc1) stable; urgency=medium
 
   * New synapse release 1.39.0rc1.
diff --git a/synapse/rest/client/v2_alpha/sync.py b/synapse/rest/client/v2_alpha/sync.py
index 7bb4e6b8aa..e321668698 100644
--- a/synapse/rest/client/v2_alpha/sync.py
+++ b/synapse/rest/client/v2_alpha/sync.py
@@ -252,10 +252,13 @@ class SyncRestServlet(RestServlet):
         if sync_result.device_lists.left:
             response["device_lists"]["left"] = list(sync_result.device_lists.left)
 
-        if sync_result.device_one_time_keys_count:
-            response[
-                "device_one_time_keys_count"
-            ] = sync_result.device_one_time_keys_count
+        # We always include this because https://github.com/vector-im/element-android/issues/3725
+        # The spec isn't terribly clear on when this can be omitted and how a client would tell
+        # the difference between "no keys present" and "nothing changed" in terms of whole field
+        # absent / individual key type entry absent
+        # Corresponding synapse issue: https://github.com/matrix-org/synapse/issues/10456
+        response["device_one_time_keys_count"] = sync_result.device_one_time_keys_count
+
         if sync_result.device_unused_fallback_key_types:
             response[
                 "org.matrix.msc2732.device_unused_fallback_key_types"