diff --git a/tests/test_services_backup.py b/tests/test_services_backup.py
index e5d2aa4..b58afee 100644
--- a/tests/test_services_backup.py
+++ b/tests/test_services_backup.py
@@ -242,9 +242,13 @@ def test_the_column_guard_covers_every_table_with_a_row_helper():
     with a new helper, and not to the registry, would be unguarded and look
     guarded. Join tables have no model class and carry both their columns by
     construction, so they are the only permitted absences."""
+    # REAL table names, as _BACKED_UP holds them — not the shorter keys the
+    # payload uses for the same sections. Getting this wrong is what the guard
+    # caught on its own first run.
     join_tables = {
-        "rulebook_subscriptions", "rule_suppressions",
-        "topic_suppressions", "rulebook_exclusions", "rule_systems",
+        "project_rulebook_subscriptions", "project_rule_suppressions",
+        "project_topic_suppressions", "project_rulebook_exclusions",
+        "rule_systems",
     }
     covered = set(_column_guard_targets()) | join_tables
     assert set(backup._BACKED_UP) - covered == set()