diff --git a/lib/lua/src/lbaselib.c b/lib/lua/src/lbaselib.c
index 2ab550bd4..ed293ebdc 100644
--- a/lib/lua/src/lbaselib.c
+++ b/lib/lua/src/lbaselib.c
@@ -340,13 +340,14 @@ static int luaB_assert (lua_State *L) {
 
 
 static int luaB_unpack (lua_State *L) {
-  int i, e, n;
+  int i, e;
+  unsigned int n;
   luaL_checktype(L, 1, LUA_TTABLE);
   i = luaL_optint(L, 2, 1);
   e = luaL_opt(L, luaL_checkint, 3, luaL_getn(L, 1));
   if (i > e) return 0;  /* empty range */
-  n = e - i + 1;  /* number of elements */
-  if (n <= 0 || !lua_checkstack(L, n))  /* n <= 0 means arith. overflow */
+  n = (unsigned int)e - (unsigned int)i;  /* number of elements minus 1 */
+  if (n > (INT_MAX - 10) || !lua_checkstack(L, ++n))
     return luaL_error(L, "too many results to unpack");
   lua_rawgeti(L, 1, i);  /* push arg[i] (avoiding overflow problems) */
   while (i++ < e)  /* push arg[i + 1...e] */