Change address of old backup

I have a backup of a very old wallet from 2011 and I imported it from bitcoin-qt into bitcoin core, but it seems like there is only one address and there is no change address in the imported data.
Does current Bitcoin Core partially import wallets?
Did bitcoin-qt in 2011 create a change address in a different way?
I searched, and the information I found was mainly about a much newer version of the wallet than the one bitcoin-qt was using.
Update: Using pywallet, I was able to retrieve and import the additional 102 addresses in my wallet. We are currently rescanning.