diff --git a/lib/merge.ex b/lib/merge.ex
index 68e19af4..2f414864 100644
--- a/lib/merge.ex
+++ b/lib/merge.ex
@@ -87,7 +87,7 @@ defmodule AshPostgres.Merge do
 
   defp do_merge(repo, resource, entries, opts) do
     table = Keyword.fetch!(opts, :table)
-    prefix = opts[:prefix]
+    prefix = opts[:prefix] || repo.default_options(:insert_all)[:prefix]
 
     # 1. USING (VALUES ...) AS EXCLUDED(cols) -- rendered, dumped, and cast by Ecto.
     {values_sql, values_params} =
diff --git a/lib/upsert.ex b/lib/upsert.ex
index fd2825f1..a4bcdefb 100644
--- a/lib/upsert.ex
+++ b/lib/upsert.ex
@@ -74,7 +74,7 @@ defmodule AshPostgres.Upsert do
 
   defp do_insert_all(repo, resource, entries, opts) do
     table = Keyword.fetch!(opts, :table)
-    prefix = opts[:prefix]
+    prefix = opts[:prefix] || repo.default_options(:insert_all)[:prefix]
 
     # 1. (cols) VALUES ($1, $2, DEFAULT), ... -- values dumped through the resource's Ecto schema.
     {header, values_sql, values_params, counter} = build_values(repo, resource, entries)