Why is narrowing conversion not preventing this map.insert() of an incorrect type from failing?

Background

When inserting a std::pair<uint64_t, uint64_t> to a C++ std::map<uint64_t, int>, neither the compiler nor the program complains, even if the passed values are not possible for the data type uint64_t.

In other words, the narrowing conversion of std::pair<uint64_t, uint64_t>(2, -2) isn't working and is defaulting to the map's type std::map<uint64_t, int>

Code

When I compile and execute the following code with g++ -Wall -Wconversion -Wextra -pedantic test/test_wrong_insert.cpp && ./a.out:

#include<map>
#include<iostream>

void print_map(std::map<uint64_t, int> & m){
  std::cout << "The map is now: {";
  for (const auto & n: m){
    std::cout << '(' << n.first << ',' << n.second << ") ";
  }
  std::cout << "}\n";
}

int main(){
  std::map<uint64_t, int> m;

  ret = m.insert(std::pair<uint64_t, uint64_t>(2,-2));
  std::cout << "Tried to insert std::pair<uint64_t, uint64_t>(2,-2). ";
  std::cout << "Return: " << ret.second << '\n';
  print_map(m);
}

Result

... this is the output:

Tried to insert std::pair<uint64_t, uint64_t>(2,-2). Return: 1
The map is now: {(2,-2) }

Question

Why does std::pair<uint64_t,uint64_t> x{-1,-2} not produce an error, and how do I make it cause an error?