diff --git a/backend/scripts/backfill_usage.py b/backend/scripts/backfill_usage.py
index e83a8b73..2c5b11c0 100644
--- a/backend/scripts/backfill_usage.py
+++ b/backend/scripts/backfill_usage.py
@@ -183,11 +183,16 @@ def backfill_personas(db, dry_run: bool) -> int:
     for persona in personas:
         persona_id = str(persona["_id"])
 
+        def _to_str(v):
+            if isinstance(v, list):
+                return " ".join(str(i) for i in v if i)
+            return str(v) if v else ""
+
         # Use background + description as the generation text
         text = " ".join(filter(None, [
-            persona.get("background") or "",
-            persona.get("description") or "",
-            persona.get("goals") or "",
+            _to_str(persona.get("background")),
+            _to_str(persona.get("description")),
+            _to_str(persona.get("goals")),
         ])).strip()
 
         if not text: