This was quite annoying, but thanks to Major hayden (thanks pal) I was able to resolve this issue by making a file on my Mac to make sure the bindings are there.
Make sure you close X Quartz first.
touch ~/.Xmodmap echo "clear Mod1" >> ~/.Xmodmap echo "keycode 66 = Alt_L" >> ~/.Xmodmap echo "keycode 69 = Alt_R" >> ~/.Xmodmap echo "add Mod1 = Alt_L" >> ~/.Xmodmap echo "add Mod1 = Alt_R" >> ~/.Xmodmap
Job done! Now it works nicely 😀 This might be relevant to those using xen, kvm and libvirtd in particular.