diff --git a/pyscf/grad/test/test_h2o.py b/pyscf/grad/test/test_h2o.py
index 1f5396e29b..38aeb52f09 100644
--- a/pyscf/grad/test/test_h2o.py
+++ b/pyscf/grad/test/test_h2o.py
@@ -173,4 +173,3 @@ def test_roks_b3lypg(self):
 if __name__ == "__main__":
     print("Full Tests for H2O")
     unittest.main()
-
diff --git a/pyscf/scf/_vhf.py b/pyscf/scf/_vhf.py
index f919cf871f..7f7c9efaed 100644
--- a/pyscf/scf/_vhf.py
+++ b/pyscf/scf/_vhf.py
@@ -465,7 +465,8 @@ def direct(dms, atm, bas, env, vhfopt=None, hermi=0, cart=False,
         vk = vk.reshape(dms_shape)
     return vj, vk
 
-# call all fjk for each dm, the return array has len(dms)*len(jkdescript)*ncomp components
+# call all fjk for each dm. The return has the shape
+# [len(jkdescript),len(dms),ncomp,nao,nao]
 # jkdescript: 'ij->s1kl', 'kl->s2ij', ...
 def direct_mapdm(intor, aosym, jkdescript,
                  dms, ncomp, atm, bas, env, vhfopt=None, cintopt=None,
@@ -504,11 +505,13 @@ def direct_mapdm(intor, aosym, jkdescript,
     if ncomp == 1:
         vjk = [v[0] for v in vjk]
 
-    # vjk.reshape(n_jk,n_dm,...).transpose(1,0,...)
-    if n_dm > 1 and n_jk > 1:
-        vjk = [vjk[i::n_dm] for i in range(n_dm)]
-    elif n_jk == 1 and single_dm:
-        vjk = vjk[0]
+    if single_dm:
+        if isinstance(jkdescript, str):
+            vjk = vjk[0]
+    elif isinstance(jkdescript, str):
+        vjk = numpy.asarray(vjk)
+    else: # n_jk > 1
+        vjk = [numpy.asarray(vjk[i*n_dm:(i+1)*n_dm]) for i in range(n_jk)]
     return vjk
 
 # for density matrices in dms, bind each dm to a jk operator
@@ -598,7 +601,10 @@ def nr_direct_drv(intor, aosym, jkscript,
         if out is None:
             buf = numpy.empty(vshape)
         else:
-            buf = numpy.ndarray(vshape, dtype=numpy.double, buffer=out[i])
+            buf = out[i]
+            assert buf.shape == vshape
+            assert buf.dtype == numpy.double
+            assert buf.flags.c_contiguous
         vjk.append(buf)
         dmsptr[i] = dms[i].ctypes.data_as(ctypes.c_void_p)
         vjkptr[i] = vjk[i].ctypes.data_as(ctypes.c_void_p)