diff --git a/Android.mk b/Android.mk
index 111ddd9fa..960b8f823 100644
--- a/Android.mk
+++ b/Android.mk
@@ -55,12 +55,21 @@ REQD_MASK_POLICY := $(LOCAL_PATH)/reqd_mask
 
 SYSTEM_EXT_PUBLIC_POLICY := $(SYSTEM_EXT_PUBLIC_SEPOLICY_DIRS)
 ifneq (,$(BOARD_PLAT_PUBLIC_SEPOLICY_DIR))
-  # TODO: Disallow BOARD_PLAT_*
+  # Must use new variable name for devices launched on S
+  ifdef PRODUCT_SHIPPING_API_LEVEL
+    ifneq ($(call math_gt_or_eq,$(PRODUCT_SHIPPING_API_LEVEL),31),)
+      $(error Please use SYSTEM_EXT_PUBLIC_SEPOLICY_DIRS instead of the old variable BOARD_PLAT_PUBLIC_SEPOLICY_DIR)
+    endif
+  endif
   SYSTEM_EXT_PUBLIC_POLICY += $(BOARD_PLAT_PUBLIC_SEPOLICY_DIR)
 endif
 SYSTEM_EXT_PRIVATE_POLICY := $(SYSTEM_EXT_PRIVATE_SEPOLICY_DIRS)
 ifneq (,$(BOARD_PLAT_PRIVATE_SEPOLICY_DIR))
-  # TODO: Disallow BOARD_PLAT_*
+  ifdef PRODUCT_SHIPPING_API_LEVEL
+    ifneq ($(call math_gt_or_eq,$(PRODUCT_SHIPPING_API_LEVEL),31),)
+      $(error Please use SYSTEM_EXT_PRIVATE_SEPOLICY_DIRS instead of the old variable BOARD_PLAT_PRIVATE_SEPOLICY_DIR)
+    endif
+  endif
   SYSTEM_EXT_PRIVATE_POLICY += $(BOARD_PLAT_PRIVATE_SEPOLICY_DIR)
 endif