explicit set an "optional" tag
diff --git a/Android.mk b/Android.mk
index 33f25da..c2e322e 100644
--- a/Android.mk
+++ b/Android.mk
@@ -17,6 +17,8 @@
 LOCAL_PATH := $(call my-dir)
 include $(CLEAR_VARS)
 
+LOCAL_MODULE_TAGS := optional
+
 LOCAL_STATIC_JAVA_LIBRARIES := libarity
 
 LOCAL_SRC_FILES := $(call all-java-files-under, src)