diff --git a/src/clib/pio_nc.c b/src/clib/pio_nc.c
index 17ca0bf3d8a..bca31c07597 100644
--- a/src/clib/pio_nc.c
+++ b/src/clib/pio_nc.c
@@ -2045,10 +2045,13 @@ int PIOc_def_var(int ncid, const char *name, nc_type xtype, int ndims,
         /* Get the MPI type corresponding with the PIO type. */
         if ((ierr = find_mpi_type(xtype, &mpi_type, NULL)))
             return pio_err(ios, NULL, ierr, __FILE__, __LINE__);
-        
+
         /* Get the size of the MPI type. */
-        if ((mpierr = MPI_Type_size(mpi_type, &mpi_type_size)))
-            return check_mpi2(ios, NULL, mpierr, __FILE__, __LINE__);
+	if(mpi_type == MPI_DATATYPE_NULL)
+	    mpi_type_size = 0;
+	else
+	    if ((mpierr = MPI_Type_size(mpi_type, &mpi_type_size)))
+		return check_mpi2(ios, NULL, mpierr, __FILE__, __LINE__);
 
         /* How many unlimited dims are present in the file? */
         if ((ierr = PIOc_inq_unlimdims(ncid, &nunlimdims, NULL)))
diff --git a/src/clib/pio_rearrange.c b/src/clib/pio_rearrange.c
index 99640236869..688b30c85eb 100644
--- a/src/clib/pio_rearrange.c
+++ b/src/clib/pio_rearrange.c
@@ -2047,9 +2047,11 @@ void performance_tune_rearranger(iosystem_desc_t *ios, io_desc_t *iodesc)
     int mpierr; /* Return code for MPI calls. */
 
     assert(iodesc);
-
-    if ((mpierr = MPI_Type_size(iodesc->mpitype, &tsize)))
-        return check_mpi(NULL, mpierr, __FILE__, __LINE__);
+    if(iodesc->mpitype == MPI_DATATYPE_NULL)
+	tsize = 0;
+    else
+	if ((mpierr = MPI_Type_size(iodesc->mpitype, &tsize)))
+	    return check_mpi(NULL, mpierr, __FILE__, __LINE__);
     cbuf = NULL;
     ibuf = NULL;
     if (iodesc->ndof > 0)
diff --git a/src/clib/pioc_support.c b/src/clib/pioc_support.c
index a514f60aec5..ae50248417a 100644
--- a/src/clib/pioc_support.c
+++ b/src/clib/pioc_support.c
@@ -691,8 +691,11 @@ int malloc_iodesc(iosystem_desc_t *ios, int piotype, int ndims,
     (*iodesc)->mpitype = mpi_type;
 
     /* Get the size of the type. */
-    if ((mpierr = MPI_Type_size((*iodesc)->mpitype, &(*iodesc)->mpitype_size)))
-        return check_mpi2(ios, NULL, mpierr, __FILE__, __LINE__);
+    if (mpi_type == MPI_DATATYPE_NULL)
+	(*iodesc)->mpitype_size = 0;
+    else
+	if ((mpierr = MPI_Type_size((*iodesc)->mpitype, &(*iodesc)->mpitype_size)))
+	    return check_mpi2(ios, NULL, mpierr, __FILE__, __LINE__);
 
     /* Initialize some values in the struct. */
     (*iodesc)->maxregions = 1;
@@ -2077,8 +2080,11 @@ int inq_file_metadata(file_desc_t *file, int ncid, int iotype, int *nvars, int *
             return pio_err(NULL, file, ret, __FILE__, __LINE__);
 
         /* Get the size of the MPI type. */
-        if ((mpierr = MPI_Type_size((*mpi_type)[v], &(*mpi_type_size)[v])))
-            return check_mpi2(NULL, file, mpierr, __FILE__, __LINE__);
+	if ((*mpi_type)[v] == MPI_DATATYPE_NULL)
+	    (*mpi_type_size)[v] = 0;
+	else
+	    if ((mpierr = MPI_Type_size((*mpi_type)[v], &(*mpi_type_size)[v])))
+		return check_mpi2(NULL, file, mpierr, __FILE__, __LINE__);
 
         /* What are the dimids associated with this var? */
         if (var_ndims)