diff --git a/CHANGES.md b/CHANGES.md
index 8a068ae8c..4c413b72e 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,3 +1,12 @@
+Synapse 1.9.1 (2020-01-28)
+==========================
+
+Bugfixes
+--------
+
+- Fix bug where setting `mau_limit_reserved_threepids` config would cause Synapse to refuse to start. ([\#6793](https://github.com/matrix-org/synapse/issues/6793))
+
+
 Synapse 1.9.0 (2020-01-23)
 ==========================
 
diff --git a/debian/changelog b/debian/changelog
index 49f318769..74eb29c5e 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,9 @@
+matrix-synapse-py3 (1.9.1) stable; urgency=medium
+
+  * New synapse release 1.9.1.
+
+ -- Synapse Packaging team <packages@matrix.org>  Tue, 28 Jan 2020 13:09:23 +0000
+
 matrix-synapse-py3 (1.9.0) stable; urgency=medium
 
   * New synapse release 1.9.0.
diff --git a/synapse/__init__.py b/synapse/__init__.py
index 6236e13aa..a236888d3 100644
--- a/synapse/__init__.py
+++ b/synapse/__init__.py
@@ -36,7 +36,7 @@ try:
 except ImportError:
     pass
 
-__version__ = "1.9.0"
+__version__ = "1.9.1"
 
 if bool(os.environ.get("SYNAPSE_TEST_PATCH_LOG_CONTEXTS", False)):
     # We import here so that we don't have to install a bunch of deps when
diff --git a/synapse/storage/data_stores/main/monthly_active_users.py b/synapse/storage/data_stores/main/monthly_active_users.py
index 89a41542a..1507a14e0 100644
--- a/synapse/storage/data_stores/main/monthly_active_users.py
+++ b/synapse/storage/data_stores/main/monthly_active_users.py
@@ -121,7 +121,13 @@ class MonthlyActiveUsersStore(MonthlyActiveUsersWorkerStore):
             if user_id:
                 is_support = self.is_support_user_txn(txn, user_id)
                 if not is_support:
-                    self.upsert_monthly_active_user_txn(txn, user_id)
+                    # We do this manually here to avoid hitting #6791
+                    self.db.simple_upsert_txn(
+                        txn,
+                        table="monthly_active_users",
+                        keyvalues={"user_id": user_id},
+                        values={"timestamp": int(self._clock.time_msec())},
+                    )
             else:
                 logger.warning("mau limit reserved threepid %s not found in db" % tp)