--- old/make/Main.gmk	2016-12-07 23:01:28.000000000 -0800
+++ new/make/Main.gmk	2016-12-07 23:01:27.000000000 -0800
@@ -272,7 +272,7 @@
 JMOD_TARGETS := $(addsuffix -jmod, $(JMOD_MODULES))
 
 define DeclareJmodRecipe
-  $1-jmod:
+  $1-jmod: java.base-copy
 	+($(CD) $(SRC_ROOT)/make && $(MAKE) $(MAKE_ARGS) -f CreateJmods.gmk \
 	    MODULE=$1)
 endef