diff --git a/changelog.d/6470.bugfix b/changelog.d/6470.bugfix
new file mode 100644
index 0000000000..c08b34c14c
--- /dev/null
+++ b/changelog.d/6470.bugfix
@@ -0,0 +1 @@
+Fix `synapse_port_db` not exiting with a 0 code if something went wrong during the port process.
diff --git a/scripts/synapse_port_db b/scripts/synapse_port_db
index f24b8ffe67..0007a15f59 100755
--- a/scripts/synapse_port_db
+++ b/scripts/synapse_port_db
@@ -47,6 +47,7 @@ from synapse.storage.data_stores.main.media_repository import (
 from synapse.storage.data_stores.main.registration import (
     RegistrationBackgroundUpdateStore,
 )
+from synapse.storage.data_stores.main.room import RoomBackgroundUpdateStore
 from synapse.storage.data_stores.main.roommember import RoomMemberBackgroundUpdateStore
 from synapse.storage.data_stores.main.search import SearchBackgroundUpdateStore
 from synapse.storage.data_stores.main.state import StateBackgroundUpdateStore
@@ -131,6 +132,7 @@ class Store(
     EventsBackgroundUpdatesStore,
     MediaRepositoryBackgroundUpdateStore,
     RegistrationBackgroundUpdateStore,
+    RoomBackgroundUpdateStore,
     RoomMemberBackgroundUpdateStore,
     SearchBackgroundUpdateStore,
     StateBackgroundUpdateStore,
@@ -1055,3 +1057,4 @@ if __name__ == "__main__":
     if end_error_exec_info:
         exc_type, exc_value, exc_traceback = end_error_exec_info
         traceback.print_exception(exc_type, exc_value, exc_traceback)
+        sys.exit(5)
diff --git a/synapse/storage/data_stores/main/room.py b/synapse/storage/data_stores/main/room.py
index b7f9024811..dd1f42c23a 100644
--- a/synapse/storage/data_stores/main/room.py
+++ b/synapse/storage/data_stores/main/room.py
@@ -28,6 +28,7 @@ from twisted.internet import defer
 from synapse.api.constants import EventTypes
 from synapse.api.errors import StoreError
 from synapse.storage._base import SQLBaseStore
+from synapse.storage.background_updates import BackgroundUpdateStore
 from synapse.storage.data_stores.main.search import SearchStore
 from synapse.types import ThirdPartyInstanceID
 from synapse.util.caches.descriptors import cached, cachedInlineCallbacks
@@ -360,9 +361,9 @@ class RoomWorkerStore(SQLBaseStore):
         defer.returnValue(row)
 
 
-class RoomStore(RoomWorkerStore, SearchStore):
+class RoomBackgroundUpdateStore(BackgroundUpdateStore):
     def __init__(self, db_conn, hs):
-        super(RoomStore, self).__init__(db_conn, hs)
+        super(RoomBackgroundUpdateStore, self).__init__(db_conn, hs)
 
         self.config = hs.config
 
@@ -438,6 +439,13 @@ class RoomStore(RoomWorkerStore, SearchStore):
 
         defer.returnValue(batch_size)
 
+
+class RoomStore(RoomBackgroundUpdateStore, RoomWorkerStore, SearchStore):
+    def __init__(self, db_conn, hs):
+        super(RoomStore, self).__init__(db_conn, hs)
+
+        self.config = hs.config
+
     @defer.inlineCallbacks
     def store_room(self, room_id, room_creator_user_id, is_public):
         """Stores a room.