diff --git a/opal/mca/btl/vader/btl_vader_endpoint.h b/opal/mca/btl/vader/btl_vader_endpoint.h
index 9a90feb2c6..3de9d6e477 100644
--- a/opal/mca/btl/vader/btl_vader_endpoint.h
+++ b/opal/mca/btl/vader/btl_vader_endpoint.h
@@ -11,7 +11,7 @@
  * Copyright (c) 2004-2005 The Regents of the University of California.
  *                         All rights reserved.
  * Copyright (c) 2006-2007 Voltaire. All rights reserved.
- * Copyright (c) 2012-2015 Los Alamos National Security, LLC. All rights
+ * Copyright (c) 2012-2016 Los Alamos National Security, LLC. All rights
  *                         reserved.
  * $COPYRIGHT$
  *
@@ -63,7 +63,7 @@ typedef struct mca_btl_base_endpoint_t {
 
     int32_t peer_smp_rank;  /**< my peer's SMP process rank.  Used for accessing
                              *   SMP specfic data structures. */
-    volatile uint64_t send_count;    /**< number of fragments sent to this peer */
+    volatile size_t send_count;    /**< number of fragments sent to this peer */
     char *segment_base;     /**< start of the peer's segment (in the address space
                              *   of this process) */
 
diff --git a/opal/mca/btl/vader/btl_vader_fbox.h b/opal/mca/btl/vader/btl_vader_fbox.h
index dfef75bb38..6f09cb6c51 100644
--- a/opal/mca/btl/vader/btl_vader_fbox.h
+++ b/opal/mca/btl/vader/btl_vader_fbox.h
@@ -261,7 +261,7 @@ static inline bool mca_btl_vader_check_fboxes (void)
 
 static inline void mca_btl_vader_try_fbox_setup (mca_btl_base_endpoint_t *ep, mca_btl_vader_hdr_t *hdr)
 {
-    if (OPAL_UNLIKELY(NULL == ep->fbox_out.buffer && mca_btl_vader_component.fbox_threshold == OPAL_THREAD_ADD64 ((volatile int64_t *) &ep->send_count, 1))) {
+    if (OPAL_UNLIKELY(NULL == ep->fbox_out.buffer && mca_btl_vader_component.fbox_threshold == OPAL_THREAD_ADD_SIZE_T (&ep->send_count, 1))) {
         /* protect access to mca_btl_vader_component.segment_offset */
         OPAL_THREAD_LOCK(&mca_btl_vader_component.lock);