diff --git a/ompi/mca/coll/base/coll_base_allgather.c b/ompi/mca/coll/base/coll_base_allgather.c
index 4cc3d7a4799..cafc6eac3ee 100644
--- a/ompi/mca/coll/base/coll_base_allgather.c
+++ b/ompi/mca/coll/base/coll_base_allgather.c
@@ -170,7 +170,7 @@ int ompi_coll_base_allgather_intra_bruck(const void *sbuf, int scount,
         char *free_buf = NULL, *shift_buf = NULL;
         ptrdiff_t span, gap;
 
-        span = opal_datatype_span(&rdtype->super, (size - rank) * rcount, &gap);
+        span = opal_datatype_span(&rdtype->super, (int64_t)(size - rank) * rcount, &gap);
 
         free_buf = (char*)calloc(span, sizeof(char));
         if (NULL == free_buf) {
diff --git a/ompi/mca/coll/base/coll_base_alltoall.c b/ompi/mca/coll/base/coll_base_alltoall.c
index 530036f771e..b56829e9999 100644
--- a/ompi/mca/coll/base/coll_base_alltoall.c
+++ b/ompi/mca/coll/base/coll_base_alltoall.c
@@ -222,7 +222,7 @@ int ompi_coll_base_alltoall_intra_bruck(const void *sbuf, int scount,
     err = ompi_datatype_type_extent (rdtype, &rext);
     if (err != MPI_SUCCESS) { line = __LINE__; goto err_hndl; }
 
-    span = opal_datatype_span(&sdtype->super, size * scount, &gap);
+    span = opal_datatype_span(&sdtype->super, (int64_t)size * scount, &gap);
 
     displs = (int *) malloc(size * sizeof(int));
     if (displs == NULL) { line = __LINE__; err = -1; goto err_hndl; }
diff --git a/ompi/mca/coll/base/coll_base_gather.c b/ompi/mca/coll/base/coll_base_gather.c
index 80f7b701564..ff83c291609 100644
--- a/ompi/mca/coll/base/coll_base_gather.c
+++ b/ompi/mca/coll/base/coll_base_gather.c
@@ -12,7 +12,7 @@
  *                         All rights reserved.
  * Copyright (c) 2013      Los Alamos National Security, LLC. All Rights
  *                         reserved.
- * Copyright (c) 2015      Research Organization for Information Science
+ * Copyright (c) 2015-2016 Research Organization for Information Science
  *                         and Technology (RIST). All rights reserved.
  * $COPYRIGHT$
  *
@@ -65,13 +65,13 @@ ompi_coll_base_gather_intra_binomial(const void *sbuf, int scount,
     bmtree = data->cached_in_order_bmtree;
 
     ompi_datatype_type_extent(sdtype, &sextent);
-    ompi_datatype_type_extent(rdtype, &rextent);
-    ssize = opal_datatype_span(&sdtype->super, scount * size, &sgap);
-    rsize = opal_datatype_span(&rdtype->super, rcount * size, &rgap);
+    ssize = opal_datatype_span(&sdtype->super, (int64_t)scount * size, &sgap);
 
     vrank = (rank - root + size) % size;
 
     if (rank == root) {
+        ompi_datatype_type_extent(rdtype, &rextent);
+        rsize = opal_datatype_span(&rdtype->super, (int64_t)rcount * size, &rgap);
         if (0 == root){
             /* root on 0, just use the recv buffer */
             ptmp = (char *) rbuf;
diff --git a/ompi/mca/coll/base/coll_base_scatter.c b/ompi/mca/coll/base/coll_base_scatter.c
index 71605595e12..b86cea4ca68 100644
--- a/ompi/mca/coll/base/coll_base_scatter.c
+++ b/ompi/mca/coll/base/coll_base_scatter.c
@@ -12,7 +12,7 @@
  *                         All rights reserved.
  * Copyright (c) 2013      Los Alamos National Security, LLC. All rights
  *                         reserved.
- * Copyright (c) 2015      Research Organization for Information Science
+ * Copyright (c) 2015-2016 Research Organization for Information Science
  *                         and Technology (RIST). All rights reserved.
  * $COPYRIGHT$
  *
@@ -62,16 +62,16 @@ ompi_coll_base_scatter_intra_binomial( const void *sbuf, int scount,
     COLL_BASE_UPDATE_IN_ORDER_BMTREE( comm, base_module, root );
     bmtree = data->cached_in_order_bmtree;
 
-    ompi_datatype_type_extent(sdtype, &sextent);
     ompi_datatype_type_extent(rdtype, &rextent);
 
-    ssize = opal_datatype_span(&sdtype->super, scount * size, &sgap);
-    rsize = opal_datatype_span(&rdtype->super, rcount * size, &rgap);
+    rsize = opal_datatype_span(&rdtype->super, (int64_t)rcount * size, &rgap);
 
     vrank = (rank - root + size) % size;
     ptmp = (char *) rbuf;  /* by default suppose leaf nodes, just use rbuf */
 
     if (rank == root) {
+        ompi_datatype_type_extent(sdtype, &sextent);
+        ssize = opal_datatype_span(&sdtype->super, (int64_t)scount * size, &sgap);
         if (0 == root) {
             /* root on 0, just use the send buffer */
             ptmp = (char *) sbuf;