diff --git a/core/clear_vars.mk b/core/clear_vars.mk
index 775a1b8..5c4dbea 100644
--- a/core/clear_vars.mk
+++ b/core/clear_vars.mk
@@ -103,6 +103,7 @@
 LOCAL_BUILD_HOST_DEX:=
 LOCAL_DEX_PREOPT:=
 LOCAL_PROTOC_OPTIMIZE_TYPE:= # lite(default),micro,full
+LOCAL_PROTOC_FLAGS:=
 
 # Trim MAKEFILE_LIST so that $(call my-dir) doesn't need to
 # iterate over thousands of entries every time.