diff --git a/ltests.c b/ltests.c
index 63ad4498..164b5a25 100644
--- a/ltests.c
+++ b/ltests.c
@@ -121,7 +121,8 @@ static void warnf (void *ud, const char *msg, int tocont) {
   strcat(buff, msg);  /* add new message to current warning */
   if (!tocont) {  /* message finished? */
     lua_unlock(L);
-    if (lua_getglobal(L, "_WARN") == LUA_TNIL)
+    lua_getglobal(L, "_WARN");
+    if (!lua_toboolean(L, -1))
       lua_pop(L, 1);  /* ok, no previous unexpected warning */
     else {
       badexit("Unhandled warning in store mode: %s\naborting...\n",
@@ -1282,10 +1283,19 @@ static int getindex_aux (lua_State *L, lua_State *L1, const char **pc) {
 }
 
 
-static void pushcode (lua_State *L, int code) {
-  static const char *const codes[] = {"OK", "YIELD", "ERRRUN",
-                   "ERRSYNTAX", MEMERRMSG, "ERRGCMM", "ERRERR"};
-  lua_pushstring(L, codes[code]);
+static const char *const statcodes[] = {"OK", "YIELD", "ERRRUN",
+    "ERRSYNTAX", MEMERRMSG, "ERRGCMM", "ERRERR"};
+
+/*
+** Avoid these stat codes from being collected, to avoid possible
+** memory error when pushing them.
+*/
+static void regcodes (lua_State *L) {
+  unsigned int i;
+  for (i = 0; i < sizeof(statcodes) / sizeof(statcodes[0]); i++) {
+    lua_pushboolean(L, 1);
+    lua_setfield(L, LUA_REGISTRYINDEX, statcodes[i]);
+  }
 }
 
 
@@ -1508,7 +1518,7 @@ static int runC (lua_State *L, lua_State *L1, const char *pc) {
       lua_pushnumber(L1, (lua_Number)getnum);
     }
     else if EQ("pushstatus") {
-      pushcode(L1, status);
+      lua_pushstring(L1, statcodes[status]);
     }
     else if EQ("pushstring") {
       lua_pushstring(L1, getstring);
@@ -1710,7 +1720,7 @@ static int Cfunc (lua_State *L) {
 
 
 static int Cfunck (lua_State *L, int status, lua_KContext ctx) {
-  pushcode(L, status);
+  lua_pushstring(L, statcodes[status]);
   lua_setglobal(L, "status");
   lua_pushinteger(L, ctx);
   lua_setglobal(L, "ctx");
@@ -1865,6 +1875,9 @@ int luaB_opentests (lua_State *L) {
   void *ud;
   lua_atpanic(L, &tpanic);
   lua_setwarnf(L, &warnf, L);
+  lua_pushboolean(L, 0);
+  lua_setglobal(L, "_WARN");  /* _WARN = false */
+  regcodes(L);
   atexit(checkfinalmem);
   lua_assert(lua_getallocf(L, &ud) == debug_realloc);
   lua_assert(ud == cast_voidp(&l_memcontrol));
diff --git a/testes/coroutine.lua b/testes/coroutine.lua
index 73333c14..0a4c2ef3 100644
--- a/testes/coroutine.lua
+++ b/testes/coroutine.lua
@@ -184,7 +184,7 @@ do
   if not T then
     warn("@on")
   else   -- test library
-    assert(string.find(_WARN, "200")); _WARN = nil
+    assert(string.find(_WARN, "200")); _WARN = false
     warn("@normal")
   end
   assert(st == false and coroutine.status(co) == "dead" and msg == 111)
diff --git a/testes/gc.lua b/testes/gc.lua
index 91915c0b..80850f92 100644
--- a/testes/gc.lua
+++ b/testes/gc.lua
@@ -372,7 +372,7 @@ if T then
   warn("@on"); warn("@store")
   collectgarbage()
   assert(string.find(_WARN, "error in __gc metamethod"))
-  assert(string.match(_WARN, "@(.-)@") == "expected"); _WARN = nil
+  assert(string.match(_WARN, "@(.-)@") == "expected"); _WARN = false
   for i = 8, 10 do assert(s[i]) end
 
   for i = 1, 5 do
@@ -481,7 +481,7 @@ if T then
   u = setmetatable({}, {__gc = function () error "@expected error" end})
   u = nil
   collectgarbage()
-  assert(string.find(_WARN, "@expected error")); _WARN = nil
+  assert(string.find(_WARN, "@expected error")); _WARN = false
   warn("@normal")
 end
 
@@ -657,14 +657,14 @@ if T then
     n = n + 1
     assert(n == o[1])
     if n == 1 then
-      _WARN = nil
+      _WARN = false
     elseif n == 2 then
       assert(find(_WARN, "@expected warning"))
       lastmsg = _WARN    -- get message from previous error (first 'o')
     else
       assert(lastmsg == _WARN)  -- subsequent error messages are equal
     end
-    warn("@store"); _WARN = nil
+    warn("@store"); _WARN = false
     error"@expected warning"
   end}
   for i = 10, 1, -1 do
diff --git a/testes/locals.lua b/testes/locals.lua
index 0e5e0c74..f5e96244 100644
--- a/testes/locals.lua
+++ b/testes/locals.lua
@@ -337,7 +337,7 @@ local function endwarn ()
   if not T then
     warn("@on")          -- back to normal
   else
-    assert(_WARN == nil)
+    assert(_WARN == false)
     warn("@normal")
   end
 end
@@ -346,7 +346,7 @@ end
 local function checkwarn (msg)
   if T then
     assert(string.find(_WARN, msg))
-    _WARN = nil    -- reset variable to check next warning
+    _WARN = false    -- reset variable to check next warning
   end
 end
 
diff --git a/testes/main.lua b/testes/main.lua
index de14a088..d2d602de 100644
--- a/testes/main.lua
+++ b/testes/main.lua
@@ -393,12 +393,12 @@ if T then   -- test library?
   -- testing 'warn'
   warn("@store")
   warn("@123", "456", "789")
-  assert(_WARN == "@123456789"); _WARN = nil
+  assert(_WARN == "@123456789"); _WARN = false
 
   warn("zip", "", " ", "zap")
-  assert(_WARN == "zip zap"); _WARN = nil
+  assert(_WARN == "zip zap"); _WARN = false
   warn("ZIP", "", " ", "ZAP")
-  assert(_WARN == "ZIP ZAP"); _WARN = nil
+  assert(_WARN == "ZIP ZAP"); _WARN = false
   warn("@normal")
 end