diff --git a/CleanSpec.mk b/CleanSpec.mk
index bdd16d5f5..9d55ae56e 100644
--- a/CleanSpec.mk
+++ b/CleanSpec.mk
@@ -682,6 +682,9 @@ $(call add-clean-step, rm -rf $(PRODUCT_OUT)/system_other)
 
 $(call add-clean-step, rm -rf $(PRODUCT_OUT)/system/apex)
 
+# Migrate preopt files to system_other for some devices
+$(call add-clean-step, rm -rf $(PRODUCT_OUT)/*/*app/*/oat)
+
 # ************************************************
 # NEWER CLEAN STEPS MUST BE AT THE END OF THE LIST
 # ************************************************
diff --git a/core/dex_preopt_config.mk b/core/dex_preopt_config.mk
index 69eaea1d7..cfe918ffb 100644
--- a/core/dex_preopt_config.mk
+++ b/core/dex_preopt_config.mk
@@ -4,7 +4,8 @@ DEX_PREOPT_CONFIG := $(SOONG_OUT_DIR)/dexpreopt.config
 DEX_PREOPT_DEFAULT ?= true
 
 # The default filter for which files go into the system_other image (if it is
-# being used). To bundle everything one should set this to '%'
+# being used). Note that each pattern p here matches both '/<p>' and /system/<p>'.
+# To bundle everything one should set this to '%'.
 SYSTEM_OTHER_ODEX_FILTER ?= \
     app/% \
     priv-app/% \