diff --git a/ompi/mca/pml/ob1/pml_ob1_sendreq.h b/ompi/mca/pml/ob1/pml_ob1_sendreq.h
index 30a7783a4f..0a67f2a65e 100644
--- a/ompi/mca/pml/ob1/pml_ob1_sendreq.h
+++ b/ompi/mca/pml/ob1/pml_ob1_sendreq.h
@@ -66,8 +66,8 @@ OBJ_CLASS_DECLARATION(mca_pml_ob1_send_request_t);
 
 struct mca_pml_ob1_send_range_t {
     ompi_free_list_item_t base;
-    uint64_t range_send_offset;
-    uint64_t range_send_length;
+    size_t range_send_offset;
+    size_t range_send_length;
 };
 typedef struct mca_pml_ob1_send_range_t mca_pml_ob1_send_range_t;
 OBJ_CLASS_DECLARATION(mca_pml_ob1_send_range_t);