Does not build, use of undeclared identifier 'ENGINE_FLAGS_NO_REGISTER_ALL'

steps to repro:
Mac OSX 10.10.3
git clone https://github.com/awslabs/s2n.git
cd s2n
make

error:
s2n_random.c:213:29: error: use of undeclared identifier
      'ENGINE_FLAGS_NO_REGISTER_ALL'
        ENGINE_set_flags(e, ENGINE_FLAGS_NO_REGISTER_ALL) != 1 ||
