SSH Key Exchange Algorithm

by a vulnerability scanning I've get following issue:

Problem Description:
The Secure Shell 2 (SSH2) protocol is a presentation layer protocol used to provide secure client-server communication.

The SSH2 protocol specification requires that a SSH2 server support the diffie-hellman-group1-sha1 key exchange algorithm. This key exchange algorithm is considered strong, but faces a potential weakness in that the same prime number is used for all key exchanges.

An alternative key exchange algorithm, diffie-hellman-exchange-group-sha1, provides enhanced security by allowing for the prime number to be specified during key exchange.

The target SSH2 server supports the diffie-hellman-group1-sha1 algorithm.

Has anybody an idea how can I fix this issue?
OpenSSH_4.7p1 is running on my server.
Thanks for Help!

Karl