How do I get progress output from Aptitude?

I'm upgrading some packages using Aptitude, and I want to get some program-readable status updates. I thought I could direct dpkg --status-fd to a file I open in advance (regular file for this experiment, but ultimately a named pipe), like this:

aptitude -o 'Dpkg::Options::=--status-fd=3' install 3>dpkg-status-log

But it seems that Aptitude closes my file descriptor before it runs dpkg:

dpkg: error: unable to read filedescriptor flags for : Bad file descriptor
E: Sub-process /usr/bin/dpkg returned an error code (2)

Is there an alternative way to get some progress feedback, short of trying to parse standard output?