C++ - use std::unordered_set Key as hash output value

I want to store a set of MD5 hashes, using std::unordered_set. The struct I'm using, named MD5_HASH for instance, holds a raw buffer which represents an MD5 hash output. std::unordered_set basically uses a default hash function if one isn't provided. I don't need to perform any hash logic on top of the buffer I'm providing to std::unordered_set, due to the fact that its already the "product" of a hash function.

So, my question is basically - how can I use the key type of a std::unordered_set set as the output of the hash function, which it supposed to use?