diff --git a/gpu4pyscf/tdscf/rhf.py b/gpu4pyscf/tdscf/rhf.py
index bdeeeb37..5991902b 100644
--- a/gpu4pyscf/tdscf/rhf.py
+++ b/gpu4pyscf/tdscf/rhf.py
@@ -22,6 +22,7 @@
 from gpu4pyscf.lib.cupy_helper import contract, tag_array
 from gpu4pyscf.lib import utils
 from gpu4pyscf.lib import logger
+from gpu4pyscf.scf import _response_functions # noqa
 from pyscf import __config__
 
 REAL_EIG_THRESHOLD = tdhf_cpu.REAL_EIG_THRESHOLD