CLion is telling me that I have a undeclared identifier but I already have

#include <iostream>
#include <chrono>
#include <thread>
#include <ctime>
#include "turkey.h"

using namespace std;

// pause the program, sleep, for given number of milliseconds
void timeTick(int amount = 1000){
     this_thread::sleep_for(std::chrono::milliseconds(amount));
}

I'm working on debugging this assignment, but Clion is telling me that my 'this_thread' "use of undeclared identifier 'this_thread'" any suggestions would be great. I have the #include already but I can't seem to figure out the reason through google.