diff --git a/core/main.mk b/core/main.mk
index 8172b22..1c7706a 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -473,10 +473,10 @@
 endif	# !SDK_ONLY
 
 # Before we go and include all of the module makefiles, stash away
-# the PRODUCT_* values so you can't get to them.
-stash_product_vars:=#true
+# the PRODUCT_* values so that later we can verify they are not modified.
+stash_product_vars:=true
 ifeq ($(stash_product_vars),true)
-  $(call stash-product-vars, __STASHED, DO_NOT_USE_IN_ANDROID_MK_)
+  $(call stash-product-vars, __STASHED)
 endif
 
 ifneq ($(ONE_SHOT_MAKEFILE),)
@@ -510,8 +510,7 @@
 endif # ONE_SHOT_MAKEFILE
 
 ifeq ($(stash_product_vars),true)
-  $(call assert-product-vars, __STASHED, DO_NOT_USE_IN_ANDROID_MK_)
-  $(call restore-product-vars, __STASHED)
+  $(call assert-product-vars, __STASHED)
 endif
 
 include $(BUILD_SYSTEM)/legacy_prebuilts.mk
diff --git a/core/product.mk b/core/product.mk
index 67413f7..cea3d1c 100644
--- a/core/product.mk
+++ b/core/product.mk
@@ -190,44 +190,29 @@
 
 
 #
-# Rename the variables in _product_var_list.
+# Stash vaues of the variables in _product_var_list.
 # $(1): Renamed prefix
-# $(2): New value prefix.  The new value will be $(2)$(VARNAME)
 #
 define stash-product-vars
 $(foreach v,$(_product_var_list), \
         $(eval $(strip $(1))_$(call rot13,$(v)):=$$($$(v))) \
-        $(eval $(v):=$(2)$$(v)) \
  )
 endef
 
 #
 # Assert that the the variable stashed by stash-product-vars remains untouched.
 # $(1): The prefix as supplied to stash-product-vars
-# $(2): The expected value prefix.  The value should be $(2)$(VARNAME)
 #
 define assert-product-vars
 $(strip \
   $(eval changed_variables:=)
   $(foreach v,$(_product_var_list), \
-    $(if $(call streq,$($(v)),$(2)$(v)),, \
+    $(if $(call streq,$($(v)),$($(strip $(1))_$(call rot13,$(v)))),, \
         $(eval $(warning $(v) has been modified: $($(v)))) \
+        $(eval $(warning previous value: $($(strip $(1))_$(call rot13,$(v))))) \
         $(eval changed_variables := $(changed_variables) $(v))) \
    ) \
   $(if $(changed_variables),\
     $(eval $(error The following variables have been changed: $(changed_variables))),)
 )
 endef
-# ... $(eval $(warning $(v) $($(v)),$(2)$(v) streq-->$(call streq,$($(v)),$(2)$(v)))) \
-
-#
-# Restore the product variables as stashed by stash-product-vars
-# $(1): The prefix as supplied to stash-product-vars
-#
-define restore-product-vars
-$(foreach v,$(_product_var_list), \
-        $(eval $(v):=$($(strip $(1))_$(call rot13,$(v)))) \
-        $(eval $(strip $(1))_$(v):=) \
- )
-endef
-