diff --git a/opal/mca/btl/vader/btl_vader_fbox.h b/opal/mca/btl/vader/btl_vader_fbox.h
index f85a5f6a22..5af802781e 100644
--- a/opal/mca/btl/vader/btl_vader_fbox.h
+++ b/opal/mca/btl/vader/btl_vader_fbox.h
@@ -56,6 +56,16 @@ static inline void mca_btl_vader_fbox_set_header (mca_btl_vader_fbox_hdr_t *hdr,
     hdr->data.tag = tag;
 }
 
+static inline mca_btl_vader_fbox_hdr_t mca_btl_vader_fbox_read_header (mca_btl_vader_fbox_hdr_t *hdr)
+{
+    mca_btl_vader_fbox_hdr_t tmp;
+    uint16_t tag = hdr->data.tag;
+    opal_atomic_rmb ();
+    tmp.ival = hdr->ival;
+    tmp.data.tag = tag;
+    return tmp;
+}
+
 /* attempt to reserve a contiguous segment from the remote ep */
 static inline bool mca_btl_vader_fbox_sendi (mca_btl_base_endpoint_t *ep, unsigned char tag,
                                              void * restrict header, const size_t header_size,
@@ -175,7 +185,7 @@ static inline bool mca_btl_vader_check_fboxes (void)
         int poll_count;
 
         for (poll_count = 0 ; poll_count <= MCA_BTL_VADER_POLL_COUNT ; ++poll_count) {
-            const mca_btl_vader_fbox_hdr_t hdr = {.ival = MCA_BTL_VADER_FBOX_HDR(ep->fbox_in.buffer + start)->ival};
+            const mca_btl_vader_fbox_hdr_t hdr = mca_btl_vader_fbox_read_header (MCA_BTL_VADER_FBOX_HDR(ep->fbox_in.buffer + start));
 
             /* check for a valid tag a sequence number */
             if (0 == hdr.data.tag || hdr.data.seq != ep->fbox_in.seq) {
diff --git a/opal/mca/btl/vader/btl_vader_fifo.h b/opal/mca/btl/vader/btl_vader_fifo.h
index 0dc70bc8a1..178a416704 100644
--- a/opal/mca/btl/vader/btl_vader_fifo.h
+++ b/opal/mca/btl/vader/btl_vader_fifo.h
@@ -12,7 +12,7 @@
  *                         All rights reserved.
  * Copyright (c) 2006-2007 Voltaire. All rights reserved.
  * Copyright (c) 2009-2010 Cisco Systems, Inc.  All rights reserved.
- * Copyright (c) 2010-2017 Los Alamos National Security, LLC.
+ * Copyright (c) 2010-2018 Los Alamos National Security, LLC.
  *                         All rights reserved.
  * $COPYRIGHT$
  *
@@ -155,7 +155,11 @@ static inline mca_btl_vader_hdr_t *vader_fifo_read (vader_fifo_t *fifo, struct m
 
 static inline void vader_fifo_init (vader_fifo_t *fifo)
 {
-    fifo->fifo_head = fifo->fifo_tail = VADER_FIFO_FREE;
+    /* due to a compiler bug in Oracle C 5.15 the following line was broken into two. Not
+     * ideal but oh well. See #5814 */
+    /* fifo->fifo_head = fifo->fifo_tail = VADER_FIFO_FREE; */
+    fifo->fifo_head = VADER_FIFO_FREE;
+    fifo->fifo_tail = VADER_FIFO_FREE;
     fifo->fbox_available = mca_btl_vader_component.fbox_max;
     mca_btl_vader_component.my_fifo = fifo;
 }