diff --git a/changelog.d/14243.bugfix b/changelog.d/14243.bugfix
new file mode 100644
index 000000000000..ac0b21c2c5f9
--- /dev/null
+++ b/changelog.d/14243.bugfix
@@ -0,0 +1 @@
+Fix a bug introduced in Synapse 1.64.0 where presence updates could be missing from `/sync` responses.
diff --git a/synapse/storage/databases/main/roommember.py b/synapse/storage/databases/main/roommember.py
index 32e1e983a5da..ab708b0ba599 100644
--- a/synapse/storage/databases/main/roommember.py
+++ b/synapse/storage/databases/main/roommember.py
@@ -742,7 +742,7 @@ def do_users_share_a_room_txn(
             # user and the set of other users, and then checking if there is any
             # overlap.
             sql = f"""
-                SELECT b.state_key
+                SELECT DISTINCT b.state_key
                 FROM (
                     SELECT room_id FROM current_state_events
                     WHERE type = 'm.room.member' AND membership = 'join' AND state_key = ?
@@ -751,7 +751,6 @@ def do_users_share_a_room_txn(
                     SELECT room_id, state_key FROM current_state_events
                     WHERE type = 'm.room.member' AND membership = 'join' AND {clause}
                 ) AS b using (room_id)
-                LIMIT 1
             """
 
             txn.execute(sql, (user_id, *args))