Blood-Cursed Knight losing lifelink

I just noticed what I think is a bug for Blood Cursed Knight.
I had a support in play when I first cast him, and he gained lifelink, as expected.
Even after the support was lost, he kept lifelink.
But, when I reinforced it (still with no support), it lost lifelink.

It seems like it should keep lifelink if it already had it when it's reinforced, right?