diff -up lua-5.4.0/src/ldo.c.bug2 lua-5.4.0/src/ldo.c

--- lua-5.4.0/src/ldo.c.bug2	2020-07-31 10:40:55.409594540 -0400

+++ lua-5.4.0/src/ldo.c	2020-07-31 10:41:19.193556341 -0400

@@ -674,7 +674,7 @@ LUA_API int lua_resume (lua_State *L, lu

   if (from == NULL)

     L->nCcalls = CSTACKTHREAD;

   else  /* correct 'nCcalls' for this thread */

-    L->nCcalls = getCcalls(from) + from->nci - L->nci - CSTACKCF;

+    L->nCcalls = getCcalls(from) - L->nci - CSTACKCF;

   if (L->nCcalls <= CSTACKERR)

     return resume_error(L, "C stack overflow", nargs);

   luai_userstateresume(L, nargs);