diff --git a/3rd/lua/lua.h b/3rd/lua/lua.h
index 747a372a..313e4cd0 100644
--- a/3rd/lua/lua.h
+++ b/3rd/lua/lua.h
@@ -460,7 +460,7 @@ struct lua_Debug {
 
 /* Add by skynet */
 
-extern lua_State * skynet_sig_L;
+LUA_API lua_State * skynet_sig_L;
 LUA_API void (lua_checksig_)(lua_State *L);
 #define lua_checksig(L) if (skynet_sig_L) { lua_checksig_(L); }