diff -Nrua /usr/ports/net/unison/patches/patch-bytearray_stubs_c ./patches/patch-bytearray_stubs_c
--- /usr/ports/net/unison/patches/patch-bytearray_stubs_c	Thu Jan  1 01:00:00 1970
+++ ./patches/patch-bytearray_stubs_c	Tue Jan 17 08:44:39 2017
@@ -0,0 +1,45 @@
+Fix rare SIGSEGV when transferring large replicas.
+Fix a theoretical integer overflow. 
+
+Patches from here:
+https://caml.inria.fr/mantis/view.php?id=7431#c17026
+and here:
+https://caml.inria.fr/mantis/view.php?id=7431#c16962
+
+Related issue reports:
+https://github.com/bcpierce00/unison/issues/48
+https://caml.inria.fr/mantis/view.php?id=7431
+https://bugzilla.redhat.com/show_bug.cgi?id=1401759
+
+Thanks to Alex Markley and OCaml developers
+--- bytearray_stubs.c.orig	Tue Jan 17 08:41:00 2017
++++ bytearray_stubs.c	Tue Jan 17 08:41:21 2017
+@@ -5,6 +5,7 @@
+ 
+ #include "caml/intext.h"
+ #include "caml/bigarray.h"
++#include "caml/memory.h"
+ 
+ CAMLprim value ml_marshal_to_bigarray(value v, value flags)
+ {
+@@ -21,15 +22,18 @@ CAMLprim value ml_marshal_to_bigarray(value v, value f
+ 
+ CAMLprim value ml_unmarshal_from_bigarray(value b, value ofs)
+ {
++  CAMLparam1(b); /* Holds [b] live until unmarshalling completes. */
++  value result;
+   struct caml_bigarray *b_arr = Bigarray_val(b);
+-  return input_value_from_block (Array_data (b_arr, ofs),
++  result = input_value_from_block (Array_data (b_arr, ofs),
+                                  b_arr->dim[0] - Long_val(ofs));
++  CAMLreturn(result);
+ }
+ 
+ CAMLprim value ml_blit_string_to_bigarray
+ (value s, value i, value a, value j, value l)
+ {
+-  char *src = String_val(s) + Int_val(i);
++  char *src = String_val(s) + Long_val(i);
+   char *dest = Array_data(Bigarray_val(a), j);
+   memcpy(dest, src, Long_val(l));
+   return Val_unit;