diff --git a/backend/app/services/site_finder/weight_profiles.py b/backend/app/services/site_finder/weight_profiles.py
index 07dc2413..7f3f0ad2 100644
--- a/backend/app/services/site_finder/weight_profiles.py
+++ b/backend/app/services/site_finder/weight_profiles.py
@@ -99,7 +99,7 @@ _INSERT = """
     INSERT INTO user_weight_profiles
         (user_id, profile_name, weights, is_default, description)
     VALUES
-        (:user_id, :profile_name, :weights::jsonb, :is_default, :description)
+        (:user_id, :profile_name, CAST(:weights AS jsonb), :is_default, :description)
     RETURNING id, created_at, updated_at
 """
 
@@ -270,7 +270,7 @@ def update_profile(
         params["profile_name"] = payload.profile_name
 
     if payload.weights is not None:
-        sets.append("weights = :weights::jsonb")
+        sets.append("weights = CAST(:weights AS jsonb)")
         params["weights"] = json.dumps(payload.weights, ensure_ascii=False)
 
     if payload.description is not None: