diff --git a/buildconfigs/Rules.mk b/buildconfigs/Rules.mk
index 26ee89472b..61cd156027 100644
--- a/buildconfigs/Rules.mk
+++ b/buildconfigs/Rules.mk
@@ -110,7 +110,12 @@ endif
 %-config:
 	$(MAKE) -f buildconfigs/mk.$* config
 
-linux-2.6-xen.patch: linux-$(LINUX_VER)-xen.patch
+linux-2.6-xen.patch: ref-linux-$(LINUX_VER)/.valid-ref
+	rm -rf tmp-$@
+	cp -al $(<D) tmp-$@
+	( cd linux-2.6-xen-sparse && ./mkbuildtree ../tmp-$@ )	
+	diff -Nurp $(<D) tmp-$@ > $@ || true
+	rm -rf tmp-$@
 
 %-xen.patch: ref-%/.valid-ref
 	rm -rf tmp-$@