Does Unity 5 support OSX i386 plugins (without x86_64)?

I'm attempting to port a custom plugin to OSX (it's running on Windows currently), and there is a dependent plugin that sits underneath my own. This dependent plugin is only built for the i386 architecture and I do not have source code access to rebuild it myself. As a result I have to build my own plugin for just i386 as well, but this results in Unity complaining that there is no image in the bundle that suits the architecture Unity is looking for (which apparently is x86_64, I'm assuming).

My question is thus: What are my options with Unity to integrate an i386 plugin that cannot be built for x86_64 as well?

Thanks in advance to anyone willing to spend time and effort on my question!