rand() in MinGW g++

I have a basic C++ file like so:

#include <iostream>

using namespace std;

int main() {
    float x = rand();
    cout << x << endl;
    return 0;
}

When I run this through g++ on Ubuntu with g++ test.cpp -o test -std=c++11, I get no errors, and the program runs just fine. But when I run it through g++ on MinGW with the same command, I get the following error:

test.cpp: In function 'int main()':
test.cpp:6:17: error: 'rand' was not declared in this scope
  float x = rand();
                 ^

I have GCC version 5.3.0. Attempting to compile with g++ test.cpp -o test.exe -std=gnu++11 does not work either.