Question Update error: unknown option --add-architecture on Ubuntu 14.04

[sfa]

I'm running Plesk 12.5.30 Update #79 on Ubuntu 14.04.6.

Unfortunately, automatic updates fail. The log says:

Registering i386 architecture support
dpkg: error: unknown option --add-architecture

Type dpkg --help for help about installing and deinstalling packages [*];
Use `dselect' or `aptitude' for user-friendly package management;
Type dpkg -Dhelp for a list of dpkg debug flag values;
Type dpkg --force-help for a list of forcing options;
Type dpkg-deb --help for help about manipulating *.deb files;

Options marked [*] produce a lot of output - pipe it through `less' or `more' !

ERROR: Unable to add i386 architecture. Please, run command `/usr/bin/dpkg --add-architecture i386` manually and restart installation or upgrade.
Not all packages were installed.
Please try to install packages again later.
Please resolve this issue and try to install the packages again.
If you cannot resolve the issue on your own, contact product technical support for assistance.

I understand that the --add-architecture option is not implemented for dpkg under Ubuntu 14.04. I have hence manually added i386 by

sudo sh -c "echo 'foreign-architecture i386' > /etc/dpkg/dpkg.cfg.d/multiarch"

So now I do get

dpkg --print-architecture
amd64
dpkg --print-foreign-architectures
i386

But this doesn't help me since the Plesk updater is still trying to run dpkg --add-architecture. Is there any way for me to edit the update scripts to remove that line or any different solution to this?

Thanks in advance.