diff --git a/synapse/storage/data_stores/main/ui_auth.py b/synapse/storage/data_stores/main/ui_auth.py
index 0d179f375807..9245e9ce2e2c 100644
--- a/synapse/storage/data_stores/main/ui_auth.py
+++ b/synapse/storage/data_stores/main/ui_auth.py
@@ -94,13 +94,10 @@ async def mark_stage_complete(
             stage_type: The completed stage type.
             identity: The identity authenticated by the stage.
         """
-        await self.db.simple_insert(
+        await self.db.simple_upsert(
             table="ui_auth_sessions_credentials",
-            values={
-                "session_id": session_id,
-                "stage_type": stage_type,
-                "identity": json.dumps(identity),
-            },
+            keyvalues={"session_id": session_id, "stage_type": stage_type},
+            values={"identity": json.dumps(identity)},
             desc="mark_stage_complete",
         )