diff --git a/CHANGELOG.md b/CHANGELOG.md
index 28542edc98..c4fa9b6a4d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,7 +3,7 @@ Changelog
 
 All notable changes to this project will be documented in this file.
 
-## [4.2.21] - UNRELEASED
+## [4.2.21] - 2024-12-03
 
 ### Fixed
 
diff --git a/docker-compose.yml b/docker-compose.yml
index 6d887d2de4..e426250a23 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -56,7 +56,7 @@ services:
 
   web:
     build: .
-    image: ghcr.io/mastodon/mastodon:v4.1.20
+    image: ghcr.io/mastodon/mastodon:v4.1.21
     restart: always
     env_file: .env.production
     command: bash -c "rm -f /mastodon/tmp/pids/server.pid; bundle exec rails s -p 3000"
@@ -77,7 +77,7 @@ services:
 
   streaming:
     build: .
-    image: ghcr.io/mastodon/mastodon:v4.1.20
+    image: ghcr.io/mastodon/mastodon:v4.1.21
     restart: always
     env_file: .env.production
     command: node ./streaming
@@ -95,7 +95,7 @@ services:
 
   sidekiq:
     build: .
-    image: ghcr.io/mastodon/mastodon:v4.1.20
+    image: ghcr.io/mastodon/mastodon:v4.1.21
     restart: always
     env_file: .env.production
     command: bundle exec sidekiq
diff --git a/lib/mastodon/version.rb b/lib/mastodon/version.rb
index 53896c0287..9dd0a53d5e 100644
--- a/lib/mastodon/version.rb
+++ b/lib/mastodon/version.rb
@@ -13,7 +13,7 @@ module Mastodon
     end
 
     def patch
-      20
+      21
     end
 
     def flags