diff --git a/xen/common/Makefile b/xen/common/Makefile
index 91581e1815..06881d023c 100644
--- a/xen/common/Makefile
+++ b/xen/common/Makefile
@@ -75,7 +75,8 @@ obj-$(CONFIG_UBSAN) += ubsan/
 obj-$(CONFIG_NEEDS_LIBELF) += libelf/
 obj-$(CONFIG_HAS_DEVICE_TREE) += libfdt/
 
-config.gz: ../.config
+CONF_FILE := $(if $(patsubst /%,,$(KCONFIG_CONFIG)),$(XEN_ROOT)/xen/)$(KCONFIG_CONFIG)
+config.gz: $(CONF_FILE)
 	gzip -c $< >$@
 
 config_data.o: config.gz