‘vector’ in namespace ‘std’ does not have a template type

So, I have a definition in my header file:

std::vector<char> showBytes(char const* fileName);

And it keeps giving me this error when I try to compile the program:

error: 'vector' in namespace 'std' does not name a template type

Any clue why it’s giving me this?

Edit:

#include <vector>
#include "file.h"

std::vector<char> showBytes(char const* fileName) {
    std::ifstream ifs(fileName, std::ios::binary|std::ios::ate);
    std::ifstream::pos_type pos = ifs.tellg();

    std::vector<char> result(pos);

    ifs.seekg(0, std::ios::beg);
    ifs.read(&result[0], pos);

    return result;
}

File.h

std::vector<char> showBytes(char const* fileName);