diff --git a/synapse/handlers/presence.py b/synapse/handlers/presence.py
index 9cc94287b..e562a2e87 100644
--- a/synapse/handlers/presence.py
+++ b/synapse/handlers/presence.py
@@ -1174,7 +1174,10 @@ def handle_timeout(state, is_mine, syncing_user_ids, now):
         # If there are have been no sync for a while (and none ongoing),
         # set presence to offline
         if user_id not in syncing_user_ids:
-            if now - state.last_user_sync_ts > SYNC_ONLINE_TIMEOUT:
+            # If the user has done something recently but hasn't synced,
+            # don't set them as offline.
+            sync_or_active = max(state.last_user_sync_ts, state.last_active_ts)
+            if now - sync_or_active > SYNC_ONLINE_TIMEOUT:
                 state = state.copy_and_replace(
                     state=PresenceState.OFFLINE,
                     status_msg=None,
diff --git a/tests/handlers/test_presence.py b/tests/handlers/test_presence.py
index d9e8f634a..de06a6ad3 100644
--- a/tests/handlers/test_presence.py
+++ b/tests/handlers/test_presence.py
@@ -324,7 +324,7 @@ class PresenceTimeoutTestCase(unittest.TestCase):
         state = UserPresenceState.default(user_id)
         state = state.copy_and_replace(
             state=PresenceState.ONLINE,
-            last_active_ts=now,
+            last_active_ts=0,
             last_user_sync_ts=now - SYNC_ONLINE_TIMEOUT - 1,
         )