--- a/make/Main.gmk	Wed Nov 29 10:35:50 2017 -0800
+++ b/make/Main.gmk	Wed Nov 29 21:23:57 2017 +0100
@@ -480,8 +480,7 @@
 #
 
 prepare-test-image:
-	$(MKDIR) -p $(TEST_IMAGE_DIR)
-	$(ECHO) > $(TEST_IMAGE_DIR)/Readme.txt 'JDK test image'
+	+($(CD) $(TOPDIR)/make && $(MAKE) $(MAKE_ARGS) -f TestImage.gmk prepare-test-image)
 
 build-test-hotspot-jtreg-native:
 	+($(CD) $(TOPDIR)/make/test && $(MAKE) $(MAKE_ARGS) -f JtregNativeHotspot.gmk \