[luacompat] luaL_pushfail() was actually introduced with Lua 5.3.

luacompat.h

@@ -17,8 +17,6 @@ typedef struct {
     FILE *f;
 } luaL_Stream;
 
-#define luaL_pushfail(L) lua_pushnil(L)
-
 static inline void luaL_requiref(lua_State *L, const char *modname, lua_CFunction openf, int glb)
 {
     lua_pushstring(L, "_LOADED");
@@ -48,4 +46,9 @@ static inline void luaL_requiref(lua_State *L, const char *modname, lua_CFunctio
 }
 
 #endif
+
+#if LUA_VERSION_NUM < 503
+#define luaL_pushfail(L) lua_pushnil(L)
+#endif
+
 #endif