IPsec: diffie-hellman group in phase 2?

Config question about IPsec (IKEv1) on IOS:

According to the IOS deployment reference it should support Diffie-Hellman group 2 or 5 for AES256, SHA1 and certificate authentication for phase 1. This seems to work.

For phase 2 it says, if perfect forward secrecy is used, then the DH group for phase 2 must match phase 1. This seems to be not case. Looking at the log file on the peer, it seems that my iphone proposes no Diffie-Hellman group for phase 2 at all. If I hardwire DH group 2 or 5 on the peer for phase 2, then the iphone cannot connect.

Every helpful comment is highly appreciated

Harri