FreeBSD: socat -- diffie hellman parameter was not prime

socat reports:

In the OpenSSL address implementation the hard coded 1024
bit DH p parameter was not prime. The effective cryptographic strength
of a key exchange using these parameters was weaker than the one one
could get by using a prime p. Moreover, since there is no indication of
how these parameters were chosen, the existence of a trapdoor that makes
possible for an eavesdropper to recover the shared secret from a key
exchange that uses them cannot be ruled out.