--- BSE/vmtxel.f90.orig	2020-08-21 11:43:52.000000000 -0700
+++ BSE/vmtxel.f90	2020-08-21 11:44:23.000000000 -0700
@@ -783,7 +783,9 @@
   if (present(comm)) then
     comm_ = comm
   else
+#ifdef MPI
     comm_ = MPI_COMM_WORLD
+#endif
   end if
 
   if (this%is_master) then
@@ -835,7 +835,9 @@
   integer(HID_T) :: file_id       ! File identifier
   integer :: error
 
+#ifdef MPI
   integer :: comm_ = MPI_COMM_WORLD
+#endif
 
   PUSH_SUB(read_and_broadcast_vmtxel_data_hdf5)