--- src/lprefix.h.orig	2018-07-14 23:49:59.792621000 +0100
+++ src/lprefix.h	2018-07-14 23:50:20.856546000 +0100
@@ -7,6 +7,8 @@
 #ifndef lprefix_h
 #define lprefix_h
 
+#include <assert.h>
+#define lua_assert(c_) assert(c_)
 
 /*
 ** Allows POSIX/XSI stuff
--- src/lgc.c.orig	2017-08-31 16:15:27 UTC
+++ src/lgc.c
@@ -984,7 +984,6 @@ static l_mem atomic (lua_State *L) {
   l_mem work;
   GCObject *origweak, *origall;
   GCObject *grayagain = g->grayagain;  /* save original list */
-  lua_assert(g->ephemeron == NULL && g->weak == NULL);
   lua_assert(!iswhite(g->mainthread));
   g->gcstate = GCSinsideatomic;
   g->GCmemtrav = 0;  /* start counting work */
@@ -1061,6 +1060,7 @@ static lu_mem singlestep (lua_State *L) 
     }
     case GCSatomic: {
       lu_mem work;
+      lua_assert(g->ephemeron == NULL && g->weak == NULL);
       propagateall(g);  /* make sure gray list is empty */
       work = atomic(L);  /* work is what was traversed by 'atomic' */
       entersweep(L);