diff --git a/src/lj_api.c b/src/lj_api.c
index 18a7ecbc..84508d7d 100644
--- a/src/lj_api.c
+++ b/src/lj_api.c
@@ -591,6 +591,20 @@ LUA_API size_t lua_objlen(lua_State *L, int idx)
   }
 }
 
+LUA_API size_t lua_rawlen(lua_State *L, int idx)
+{
+  TValue *o = index2adr(L, idx);
+  if (tvisstr(o)) {
+    return strV(o)->len;
+  } else if (tvistab(o)) {
+    return (size_t)lj_tab_len(tabV(o));
+  } else if (tvisudata(o)) {
+    return udataV(o)->len;
+  } else {
+    return 0;
+  }
+}
+
 LUA_API lua_CFunction lua_tocfunction(lua_State *L, int idx)
 {
   cTValue *o = index2adr(L, idx);
diff --git a/src/lua.h b/src/lua.h
index 6d1634d1..6ffa16d0 100644
--- a/src/lua.h
+++ b/src/lua.h
@@ -352,6 +352,7 @@ LUA_API const lua_Number *lua_version (lua_State *L);
 LUA_API void lua_copy (lua_State *L, int fromidx, int toidx);
 LUA_API lua_Number lua_tonumberx (lua_State *L, int idx, int *isnum);
 LUA_API lua_Integer lua_tointegerx (lua_State *L, int idx, int *isnum);
+LUA_API size_t lua_rawlen (lua_State *L, int idx);
 
 /* From Lua 5.3. */
 LUA_API int lua_isyieldable (lua_State *L);