https://bugzilla.mozilla.org/show_bug.cgi?id=627664

diff -up xulrunner-2.0/mozilla-central/js/src/jsval.h.64bit-big-endian xulrunner-2.0/mozilla-central/js/src/jsval.h
--- xulrunner-2.0/mozilla-central/js/src/jsval.h.64bit-big-endian	2011-01-20 15:59:49.000000000 +0100
+++ xulrunner-2.0/mozilla-central/js/src/jsval.h	2011-01-20 16:00:21.000000000 +0100
@@ -347,6 +347,7 @@ typedef union jsval_layout
             int32          i32;
             uint32         u32;
             JSWhyMagic     why;
+            jsuword        word;
         } payload;
     } s;
     double asDouble;