--- a/make/lib/Lib-jdk.net.gmk	Mon Apr 16 14:51:31 2018 +0200
+++ b/make/lib/Lib-jdk.net.gmk	Wed Apr 18 14:22:53 2018 +0200
@@ -33,7 +33,8 @@
       NAME := extnet, \
       OPTIMIZATION := LOW, \
       CFLAGS := $(CFLAGS_JDKLIB), \
-      HEADER_FLAGS := -I$(SUPPORT_OUTPUTDIR)/headers/jdk.net, \
+      HEADER_FLAGS := \
+          -I$(call FindHeaderDirForModule, $(MODULE)), \
       LDFLAGS := $(LDFLAGS_JDKLIB) \
           $(call SET_SHARED_LIBRARY_ORIGIN), \
       LIBS := -ljava, \