diff --git a/zUtil_Cxx/include/gtCxxPlaceSubVolOps.h b/zUtil_Cxx/include/gtCxxPlaceSubVolOps.h
index 04720b21ef38b4eaa7e5fc8596fafe9325d7967e..7c972c00df5fd282f1329147badf0c2eea63c527 100644
--- a/zUtil_Cxx/include/gtCxxPlaceSubVolOps.h
+++ b/zUtil_Cxx/include/gtCxxPlaceSubVolOps.h
@@ -273,7 +273,7 @@ namespace GT3D {
       const mwSize sub_vol_skip_dim_2 = sub_vol_dims[0];
 
       const double * const chunk_dims_d = (double *) mxGetData(mat_chunk_dims);
-      const mwSize chunk_dims[3] = {chunk_dims_d[0], chunk_dims_d[1], chunk_dims_d[2]};
+      const mwSize chunk_dims[3] = {(mwSize)chunk_dims_d[0], (mwSize)chunk_dims_d[1], (mwSize)chunk_dims_d[2]};
 
       const mwSize line_length_unroll = ROUND_DOWN(chunk_dims[0], 4);
 
@@ -363,9 +363,9 @@ namespace GT3D {
         const mwSize sub_vol_skip_dim_2 = sub_vol_dims[0];
 
         const mwSize chunk_dims[3] = {
-            chunk_dims_d[0 * num_sub_vols + vol_num],
-            chunk_dims_d[1 * num_sub_vols + vol_num],
-            chunk_dims_d[2 * num_sub_vols + vol_num]};
+            (mwSize)chunk_dims_d[0 * num_sub_vols + vol_num],
+            (mwSize)chunk_dims_d[1 * num_sub_vols + vol_num],
+            (mwSize)chunk_dims_d[2 * num_sub_vols + vol_num]};
 
         const mwSize line_length_unroll = ROUND_DOWN(chunk_dims[0], 4);