diff --git a/src/NETCDF/dump_netcdf_mpiio.cpp b/src/NETCDF/dump_netcdf_mpiio.cpp
index 2407678386..fe65ccae18 100644
--- a/src/NETCDF/dump_netcdf_mpiio.cpp
+++ b/src/NETCDF/dump_netcdf_mpiio.cpp
@@ -639,8 +639,8 @@ void DumpNetCDFMPIIO::write()
   nme = count();
   int *block_sizes = new int[comm->nprocs];
   MPI_Allgather(&nme, 1, MPI_INT, block_sizes, 1, MPI_INT, world);
-  blocki = 0;
-  for (int i = 0; i < comm->me; i++)  blocki += block_sizes[i];
+  blocki = (MPI_Offset) 0;
+  for (int i = 0; i < comm->me; i++)  blocki += (MPI_Offset) (block_sizes[i]);
   delete[] block_sizes;
 
   // ensure buf is sized for packing and communicating
diff --git a/src/NETCDF/dump_netcdf_mpiio.h b/src/NETCDF/dump_netcdf_mpiio.h
index 14ee930e26..004c5fb209 100644
--- a/src/NETCDF/dump_netcdf_mpiio.h
+++ b/src/NETCDF/dump_netcdf_mpiio.h
@@ -49,11 +49,11 @@ class DumpNetCDFMPIIO : public DumpCustom {
     int quantity;                          // type of the quantity
   };
 
-  int framei;    // current frame index
-  int blocki;    // current block index
+  MPI_Offset framei;    // current frame index
+  MPI_Offset blocki;    // current block index
   int ndata;     // number of data blocks to expect
 
-  bigint ntotalgr;    // # of atoms
+  MPI_Offset ntotalgr;    // # of atoms
 
   int n_perat;          // # of netcdf per-atom properties
   nc_perat_t *perat;    // per-atom properties