diff --git a/core/droiddoc.mk b/core/droiddoc.mk
index 48a930d..4f5b1bc 100644
--- a/core/droiddoc.mk
+++ b/core/droiddoc.mk
@@ -166,6 +166,10 @@
 # TODO: not clear if this is used any more
 $(full_target): PRIVATE_LOCAL_PATH := $(LOCAL_PATH)
 
+# TODO(tobiast): Clean this up once we move to -source 1.9.
+# OpenJDK 9 does not have the concept of a "boot classpath" so we should
+# then rename PRIVATE_BOOTCLASSPATH to PRIVATE_MODULE or similar. For now,
+# keep -bootclasspath here since it works in combination with -source 1.8.
 $(full_target): \
         $(full_src_files) \
         $(droiddoc_templates) \
@@ -210,6 +214,18 @@
 ## standard doclet only
 ##
 ##
+
+ifneq ($(EXPERIMENTAL_USE_OPENJDK9),)
+# For OpenJDK 9 we use --patch-module to define the core libraries code.
+# TODO(tobiast): Reorganize this when adding proper support for OpenJDK 9
+# modules. Here we treat all code in core libraries as being in java.base
+# to work around the OpenJDK 9 module system. http://b/62049770
+$(full_target): PRIVATE_BOOTCLASSPATH_ARG := --patch-module=java.base=$(PRIVATE_BOOTCLASSPATH)
+else
+# For OpenJDK 8 we can use -bootclasspath to define the core libraries code.
+$(full_target): PRIVATE_BOOTCLASSPATH_ARG := $(addprefix -bootclasspath ,$(PRIVATE_BOOTCLASSPATH))
+endif
+
 $(full_target): $(full_src_files) $(full_java_lib_deps)
 	@echo Docs javadoc: $(PRIVATE_OUT_DIR)
 	@mkdir -p $(dir $@)
@@ -225,7 +241,7 @@
                 -Xdoclint:none \
                 $(PRIVATE_PROFILING_OPTIONS) \
                 $(addprefix -classpath ,$(PRIVATE_CLASSPATH)) \
-                $(addprefix -bootclasspath ,$(PRIVATE_BOOTCLASSPATH)) \
+                $(PRIVATE_BOOTCLASSPATH_ARG) \
                 -sourcepath $(PRIVATE_SOURCE_PATH)$(addprefix :,$(PRIVATE_CLASSPATH)) \
                 -d $(PRIVATE_OUT_DIR) \
                 -quiet \