Mordekaiser can use Harvester of Sorrow's (E) on Jarvan's flag???

So yeah just like it says in the title. I was playing a custom game of Dominion when I used Morde's W (couldn't tell you if I was aiming for bot Jarvan or myself sorry) and suddenly I see the partner necro field not on my ally but his flag....huh. Don't know if this is a glitch or an oversight but either way felt it should be pointed out. If anyone can reproduce the effect and show it in the comments it'd help ferret out if this was an isolated incident or not. Heck who knows maybe it'll even end up as a scurb "Did you know?". Or patched out, either way.