Grr... I really hate Internet Explorer. Crappy shit browser. Anyway, if you change line 225 in envir.c from
if (strncmp(headerfields->data, "X-", 2) == 0) {
to
if (strncasecmp(headerfields->data, "X-", 2) == 0) {
your problem will be fixed. I changed this also in the coming 8.5 release.