diff --git a/posthog/admin/admins/ducklake_backfill_admin.py b/posthog/admin/admins/ducklake_backfill_admin.py
index 9556561d0368..2bb23daf9073 100644
--- a/posthog/admin/admins/ducklake_backfill_admin.py
+++ b/posthog/admin/admins/ducklake_backfill_admin.py
@@ -18,7 +18,10 @@ class DuckLakeBackfillAdmin(admin.ModelAdmin):
     )
     list_filter = ("enabled",)
     search_fields = ("=team__id", "table_suffix")
-    readonly_fields = ("id", "created_at", "updated_at")
+    # `table_suffix` is write-once: it names a team's warehouse tables/schema, so changing it after
+    # data is written moves the target and orphans the old tables. It's set only through the
+    # validated enable flow (`enable_team_backfill`), never edited here.
+    readonly_fields = ("id", "table_suffix", "created_at", "updated_at")
     raw_id_fields = ("team", "created_by")
     actions = ("make_enabled", "make_disabled")
 
diff --git a/posthog/admin/test_ducklake_backfill_admin.py b/posthog/admin/test_ducklake_backfill_admin.py
new file mode 100644
index 000000000000..1de52cd3e014
--- /dev/null
+++ b/posthog/admin/test_ducklake_backfill_admin.py
@@ -0,0 +1,21 @@
+from posthog.test.base import BaseTest
+
+from django.contrib.admin.sites import AdminSite
+from django.test import RequestFactory
+
+from posthog.admin.admins.ducklake_backfill_admin import DuckLakeBackfillAdmin
+from posthog.models import DuckLakeBackfill
+
+
+class TestDuckLakeBackfillAdmin(BaseTest):
+    def setUp(self) -> None:
+        super().setUp()
+        self.admin = DuckLakeBackfillAdmin(DuckLakeBackfill, AdminSite())
+        self.request = RequestFactory().get("/")
+        self.request.user = self.user
+
+    def test_table_suffix_is_readonly(self) -> None:
+        # `table_suffix` is write-once — editing it in admin would move a team's warehouse
+        # schema/tables and orphan the old ones. It must never be editable here.
+        backfill = DuckLakeBackfill.objects.create(team=self.team, enabled=True, table_suffix="acme")
+        assert "table_suffix" in self.admin.get_readonly_fields(self.request, backfill)