diff --git a/plinth/modules/matrixsynapse/__init__.py b/plinth/modules/matrixsynapse/__init__.py
index 34a7cf600..4c1d39173 100644
--- a/plinth/modules/matrixsynapse/__init__.py
+++ b/plinth/modules/matrixsynapse/__init__.py
@@ -132,7 +132,7 @@ def force_upgrade(helper, packages):
 
     # Allow any lower version to upgrade to 1.8.*
     package = packages['matrix-synapse']
-    if Version(package['new_version']) > Version('1.9~'):
+    if Version(package['new_version']) > Version('1.12~'):
         return False
 
     public_registration_status = get_public_registration_status()
diff --git a/plinth/modules/upgrades/data/etc/apt/preferences.d/50freedombox3.pref b/plinth/modules/upgrades/data/etc/apt/preferences.d/50freedombox3.pref
index 918f3408e..b7a06d9cb 100644
--- a/plinth/modules/upgrades/data/etc/apt/preferences.d/50freedombox3.pref
+++ b/plinth/modules/upgrades/data/etc/apt/preferences.d/50freedombox3.pref
@@ -19,3 +19,8 @@ Explanation: matrix-synapse >= 1.5 requires python3-typing-extensions >= 3.7.4
 Package: python3-typing-extensions
 Pin: release a=buster-backports
 Pin-Priority: 500
+
+Explanation: matrix-synapse >= 1.11 requires python3-signedjson >= 1.1.0
+Package: python3-signedjson
+Pin: release a=buster-backports
+Pin-Priority: 500