diff --git a/core/definitions.mk b/core/definitions.mk
index 63b123e..f60fa0a 100644
--- a/core/definitions.mk
+++ b/core/definitions.mk
@@ -2531,6 +2531,7 @@
 $(if $(filter $(1),$(PLATFORM_VERSION_CODENAME)),10000,$(1))
 endef
 
+# --add-opens is required because desugar reflects via java.lang.invoke.MethodHandles.Lookup
 define desugar-classes-jar
 @echo Desugar: $@
 @mkdir -p $(dir $@)
@@ -2538,6 +2539,7 @@
 @rm -rf $(dir $@)/desugar_dumped_classes
 @mkdir $(dir $@)/desugar_dumped_classes
 $(hide) java \
+    $(if $(EXPERIMENTAL_USE_OPENJDK9),--add-opens java.base/java.lang.invoke=ALL-UNNAMED,) \
     -Djdk.internal.lambda.dumpProxyClasses=$(abspath $(dir $@))/desugar_dumped_classes \
     -jar $(DESUGAR) \
     $(addprefix --bootclasspath_entry ,$(call desugar-bootclasspath,$(PRIVATE_BOOTCLASSPATH))) \
@@ -2691,10 +2693,14 @@
 $(call sign-package-arg,$@)
 endef
 
+# signapk uses internal APIs from sun.security.{pkcs,x509}; see http://b/37137869
 # $(1): the package file we are signing.
 define sign-package-arg
 $(hide) mv $(1) $(1).unsigned
-$(hide) java -Djava.library.path=$(SIGNAPK_JNI_LIBRARY_PATH) -jar $(SIGNAPK_JAR) \
+$(hide) java -Djava.library.path=$(SIGNAPK_JNI_LIBRARY_PATH) \
+    $(if $(EXPERIMENTAL_USE_OPENJDK9),--add-exports java.base/sun.security.pkcs=ALL-UNNAMED,) \
+    $(if $(EXPERIMENTAL_USE_OPENJDK9),--add-exports java.base/sun.security.x509=ALL-UNNAMED,) \
+    -jar $(SIGNAPK_JAR) \
     $(PRIVATE_CERTIFICATE) $(PRIVATE_PRIVATE_KEY) \
     $(PRIVATE_ADDITIONAL_CERTIFICATES) $(1).unsigned $(1).signed
 $(hide) mv $(1).signed $(1)