diff --git a/core/board_config.mk b/core/board_config.mk
index 62d779c..597b10e 100644
--- a/core/board_config.mk
+++ b/core/board_config.mk
@@ -534,6 +534,14 @@
   TARGET_VENDOR_TEST_SUFFIX :=
 endif
 
+###########################################
+# APEXes are by default flattened, i.e. non-updatable.
+# It can be unflattened (and updatable) by inheriting from
+# updatable_apex.mk
+ifeq (,$(TARGET_FLATTEN_APEX))
+TARGET_FLATTEN_APEX := true
+endif
+
 ifeq (,$(TARGET_BUILD_APPS))
 ifdef PRODUCT_EXTRA_VNDK_VERSIONS
   $(foreach v,$(PRODUCT_EXTRA_VNDK_VERSIONS),$(call check_vndk_version,$(v)))