Index: ompi/mca/pml/ob1/pml_ob1_recvfrag.h
===================================================================
--- ompi/mca/pml/ob1/pml_ob1_recvfrag.h	(revision 27446)
+++ ompi/mca/pml/ob1/pml_ob1_recvfrag.h	(working copy)
@@ -69,7 +69,9 @@
     unsigned char* _ptr = (unsigned char*)frag->addr;                   \
     /* init recv_frag */                                                \
     frag->btl = btl;                                                    \
-    frag->hdr = *(mca_pml_ob1_hdr_t*)hdr;                               \
+    _size = (segs[0].seg_len < sizeof(mca_pml_ob1_hdr_t)) ?             \
+            segs[0].seg_len : sizeof(mca_pml_ob1_hdr_t);                \
+    memcpy( &frag->hdr, hdr, _size);                                    \
     frag->num_segments = 1;                                             \
     _size = segs[0].seg_len;                                            \
     for( i = 1; i < cnt; i++ ) {                                        \