--- contrib/subtree/Makefile.orig	2014-10-14 22:09:29.000000000 -0400
+++ contrib/subtree/Makefile	2014-10-14 22:09:43.000000000 -0400
@@ -53,7 +53,7 @@
 	$(INSTALL) -m 644 $^ $(DESTDIR)$(man1dir)
 
 $(GIT_SUBTREE_DOC): $(GIT_SUBTREE_XML)
-	$(XMLTO) -m $(MANPAGE_XSL) man $^
+	$(XMLTO) --skip-validation -m $(MANPAGE_XSL) man $^
 
 $(GIT_SUBTREE_XML): $(GIT_SUBTREE_TXT)
 	$(ASCIIDOC) -b docbook -d manpage -f $(ASCIIDOC_CONF) \
