diff --git a/pyscf/mcpdft/otfnal.py b/pyscf/mcpdft/otfnal.py
index a9581be..095bb29 100644
--- a/pyscf/mcpdft/otfnal.py
+++ b/pyscf/mcpdft/otfnal.py
@@ -68,6 +68,7 @@ def energy_ot (ot, casdm1s, casdm2, mo_coeff, ncore, max_memory=2000, hermi=1):
     ni, xctype = ot._numint, ot.xctype
     if xctype=='HF': return E_ot
     dens_deriv = ot.dens_deriv
+    Pi_deriv = ot.Pi_deriv
 
     nao = mo_coeff.shape[0]
     ncas = casdm2.shape[0]
@@ -84,7 +85,7 @@ def energy_ot (ot, casdm1s, casdm2, mo_coeff, ncore, max_memory=2000, hermi=1):
         rho = np.asarray ([m[0] (0, ao, mask, xctype) for m in make_rho])
         t0 = logger.timer (ot, 'untransformed density', *t0)
         Pi = get_ontop_pair_density (ot, rho, ao, cascm2, mo_cas,
-            dens_deriv, mask)
+            Pi_deriv, mask)
         t0 = logger.timer (ot, 'on-top pair density calculation', *t0)
         if rho.ndim == 2:
             rho = np.expand_dims (rho, 1)