diff --git a/ompi/datatype/ompi_datatype_args.c b/ompi/datatype/ompi_datatype_args.c
index f6c0851e59e..5f9e5d92daa 100644
--- a/ompi/datatype/ompi_datatype_args.c
+++ b/ompi/datatype/ompi_datatype_args.c
@@ -15,6 +15,7 @@
  *                         reserved.
  * Copyright (c) 2015-2017 Research Organization for Information Science
  *                         and Technology (RIST). All rights reserved.
+ * Copyright (c) 2017      IBM Corporation. All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -837,16 +838,19 @@ ompi_datatype_t* ompi_datatype_get_single_predefined_type_from_args( ompi_dataty
                 return NULL;
             }
         }
-        if( NULL == predef ) {  /* This is the first iteration */
-            predef = current_predef;
-        } else {
-            /**
-             *  What exactly should we consider as identical types? If they are
-             * the same MPI level type, or if they map to the same OPAL datatype?
-             * In other words, MPI_FLOAT and MPI_REAL4 are they identical?
-             */
-            if( predef != current_predef ) {
-                return NULL;
+        if (current_predef != MPI_LB && current_predef != MPI_UB) {
+            if( NULL == predef ) {  /* This is the first iteration */
+                predef = current_predef;
+            } else {
+                /**
+                 *  What exactly should we consider as identical types?
+                 *  If they are the same MPI level type, or if they map
+                 *  to the same OPAL datatype? In other words, MPI_FLOAT
+                 *  and MPI_REAL4 are they identical?
+                 */
+                if( predef != current_predef ) {
+                    return NULL;
+                }
             }
         }
     }
diff --git a/ompi/mca/osc/base/osc_base_obj_convert.c b/ompi/mca/osc/base/osc_base_obj_convert.c
index bb4641c659d..e396258ce2b 100644
--- a/ompi/mca/osc/base/osc_base_obj_convert.c
+++ b/ompi/mca/osc/base/osc_base_obj_convert.c
@@ -109,12 +109,16 @@ int ompi_osc_base_process_op (void *outbuf, void *inbuf, size_t inbuflen,
         bool done;
 
         primitive_datatype = ompi_datatype_get_single_predefined_type_from_args(datatype);
+        ompi_datatype_type_size (primitive_datatype, &primitive_size);
+
         if (ompi_datatype_is_contiguous_memory_layout (datatype, count) &&
             1 == datatype->super.desc.used) {
             /* NTH: the datatype is made up of a contiguous block of the primitive
              * datatype. fast path. do not set up a convertor to deal with the
              * datatype. */
-            count *= datatype->super.desc.desc[0].elem.count;
+            (void)ompi_datatype_type_size(datatype, &size);
+            count *= (size / primitive_size);
+            assert( 0 == (size % primitive_size) );
 
             /* in case it is possible for the datatype to have a non-zero lb in this case.
              * remove me if this is not possible */
@@ -125,8 +129,6 @@ int ompi_osc_base_process_op (void *outbuf, void *inbuf, size_t inbuflen,
             return OMPI_SUCCESS;
         }
 
-        ompi_datatype_type_size (primitive_datatype, &primitive_size);
-
         /* create convertor */
         OBJ_CONSTRUCT(&convertor, opal_convertor_t);
         opal_convertor_copy_and_prepare_for_recv(ompi_mpi_local_convertor, &datatype->super,