hkdf.h not found cryptopp

Cannot include the hkdf.h from the crypto++ library into my code.

It says cryptopp/hkdf.h not found. Although I can import other parts from the same library into my code, such as cryptopp/sha.h

I am using the g++ with the -std=c++11 and the -lcryptopp flags

I looked into the docs and it suggested the lcryptopp flag which I am using. This should not be an issue, am I missing something ?