diff --git a/data/sql/92_cad_bulk_layers.sql b/data/sql/92_cad_bulk_layers.sql
index cb5a8b83..82183634 100644
--- a/data/sql/92_cad_bulk_layers.sql
+++ b/data/sql/92_cad_bulk_layers.sql
@@ -503,6 +503,12 @@ BEGIN
         WHERE table_schema = 'public' AND table_name = 'cad_buildings'
     ) THEN
         ALTER TABLE cad_buildings_new RENAME TO cad_buildings;
+        -- First, retire the legacy PK index name that's still attached to
+        -- cad_buildings_old_apr26 (PG does NOT auto-rename PK indexes on
+        -- table rename — pre-K.1 backup left cad_buildings_pkey behind).
+        -- Without this rename, the next line collides with the existing
+        -- index name → 'relation already exists' → tx rollback.
+        ALTER INDEX IF EXISTS cad_buildings_pkey              RENAME TO cad_buildings_old_apr26_pkey;
         -- Rename indexes to drop the _new suffix
         ALTER INDEX IF EXISTS cad_buildings_new_pkey          RENAME TO cad_buildings_pkey;
         -- Note: ALTER INDEX RENAME on a PK index also renames the constraint