diff --git a/supabase/migrations/20260807000600_invoicing.sql b/supabase/migrations/20260807000600_invoicing.sql
index f7c61a5..7a704bf 100644
--- a/supabase/migrations/20260807000600_invoicing.sql
+++ b/supabase/migrations/20260807000600_invoicing.sql
@@ -450,12 +450,14 @@ BEGIN
   END LOOP;
 
   -- Step 9: outstanding credits, oldest first, never below zero.
+  -- Every column is alias-qualified: this function's RETURNS TABLE declares an
+  -- `amount_cents` output, which would otherwise shadow the table's column.
   FOR cred IN
-    SELECT * FROM public.student_credits
-    WHERE student_id = _student AND NOT is_void
-      AND amount_applied_cents < amount_cents
-      AND (expires_on IS NULL OR expires_on >= _from)
-    ORDER BY issued_at
+    SELECT sc.* FROM public.student_credits sc
+    WHERE sc.student_id = _student AND NOT sc.is_void
+      AND sc.amount_applied_cents < sc.amount_cents
+      AND (sc.expires_on IS NULL OR sc.expires_on >= _from)
+    ORDER BY sc.issued_at
   LOOP
     EXIT WHEN running_total <= 0;
     remaining := cred.amount_cents - cred.amount_applied_cents;