diff -up lua-5.3.4/src/lapi.c.bug6 lua-5.3.4/src/lapi.c

--- lua-5.3.4/src/lapi.c.bug6	2018-02-13 10:18:59.386451581 -0500

+++ lua-5.3.4/src/lapi.c	2018-02-13 10:19:42.700575448 -0500

@@ -533,6 +533,7 @@ LUA_API void lua_pushcclosure (lua_State

   lua_lock(L);

   if (n == 0) {

     setfvalue(L->top, fn);

+    api_incr_top(L);

   }

   else {

     CClosure *cl;

@@ -546,9 +547,9 @@ LUA_API void lua_pushcclosure (lua_State

       /* does not need barrier because closure is white */

     }

     setclCvalue(L, L->top, cl);

+    api_incr_top(L);

+    luaC_checkGC(L);

   }

-  api_incr_top(L);

-  luaC_checkGC(L);

   lua_unlock(L);

 }