Allocate vector size with list initialization (curly braces)

How can I do the equivelant of:

#include <vector>

size_t bufferSize = 1024 * 1024;
std::vector<unsigned char> buffer(bufferSize, ' ');

With list (curly braced) initialization?

When I try to do the following:

#include <vector>

size_t bufferSize = 1024 * 1024;
std::vector<unsigned char> buffer {bufferSize, ' '};

It wrongly interprets bufferSize as the value to be stored in the first index of the container (i.e. calls the wrong std::vector constructor), and fails to compile due to invalid narrowing conversion from unsigned int (size_t) to unsigned char.