cannot scan with cupsd+saned

[brudan]

I have OpenBSD 6.4 installed on my T400 Thinkpad. I also own an HP Photosmart 7520 all-in-one printer/scanner/copier that is connected to my home wireless network. I can print over the network, but scanning applications (both simple-scan and xsane) crash with the following error as soon as scanning begins:

bruno@thinkpad:~$ simple-scan
dbus[3472]: arguments to dbus_connection_send() were incorrect, assertion "connection != NULL" failed in file dbus-connection.c line 3307.
This is normally a bug in some application using the D-Bus library.

  D-Bus not compiled with backtrace support so unable to print a backtrace
Abort trap

Maybe I missed a step when I set things up? Here is what I did:

1.

# pkg_add pkg_add -iv hplip hplip-common hpcups hpaio system-config-printer sane-backends xsane simple-scan

2. Launch system-config-printer and added my printer, using proper HPLIP driver.

3.

# vi /etc/rc.conf.local 
pkg_scripts="cupsd cups_browsed saned"
dbus_enable=YES
cupsd_flags=""
cups_browsed_flags=""
saned_flags=""

4. Reboot

5.

$ simple-scan

I also tried running the scanning applications as root, but same crash with same error message. I tried turning off the firewall (# pfctl -d) but that made no difference either. dbus is required by my desktop environment (MATE) and I can confirm that dbus is running:

bruno@thinkpad:~$ pgrep -fl dbus
47121 /usr/local/bin/dbus-daemon --syslog-only --fork --print-pid 5 --print-address 7 --session
79834 dbus-launch --autolaunch=bcdecefff7e7bef5828bb3715c08518a --binary-syntax --close-stderr
28903 /usr/local/libexec/cups/notifier/dbus dbus:// 
47181 /usr/local/bin/dbus-daemon --config-file=/usr/local/share/defaults/at-spi2/accessibility.conf --nofork --print-address 3
23497 /usr/local/bin/dbus-daemon --syslog --fork --print-pid 6 --print-address 8 --session
40727 dbus-launch --exit-with-session mate-session

I don't know where to go from here. Any ideas? I'd like to be able to scan over wifi. I know the printer/scanner is not the problem because it works when I'm booted into my Devuan partition. I think I missed a step in configuring OpenBSD for scanning over the network.