diff --git a/core/board_config.mk b/core/board_config.mk
index 4f73547..3127c19 100644
--- a/core/board_config.mk
+++ b/core/board_config.mk
@@ -584,8 +584,16 @@
 # 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
+#
+# APEX flattening can also be forcibly enabled (resp. disabled) by
+# setting OVERRIDE_TARGET_FLATTEN_APEX to true (resp. false), e.g. by
+# setting the OVERRIDE_TARGET_FLATTEN_APEX environment variable.
+ifdef OVERRIDE_TARGET_FLATTEN_APEX
+  TARGET_FLATTEN_APEX := $(OVERRIDE_TARGET_FLATTEN_APEX)
+else
+  ifeq (,$(TARGET_FLATTEN_APEX))
+    TARGET_FLATTEN_APEX := true
+  endif
 endif
 
 ifeq (,$(TARGET_BUILD_APPS))