Index: root/xen-unstable.hg/tools/libxc/xc_domain_save.c
===================================================================
--- root.orig/xen-unstable.hg/tools/libxc/xc_domain_save.c
+++ root/xen-unstable.hg/tools/libxc/xc_domain_save.c
@@ -1597,6 +1597,8 @@ int xc_domain_save(int xc_handle, int io
         domctl.cmd = XEN_DOMCTL_get_ext_vcpucontext;
         domctl.domain = dom;
         domctl.u.ext_vcpucontext.vcpu = i;
+        domctl.u.ext_vcpucontext.size = sizeof(domctl.u.ext_vcpucontext);
+
         if ( xc_domctl(xc_handle, &domctl) < 0 )
         {
             ERROR("No extended context for VCPU%d", i);