Vulnerability skill + Hand of chayula + Decaying Hex works but message says it shouldn't.

I just got the Hand of chayula ability and socketed in the vulnerability skill. After which I wanted to see if I could socket in the decaying hex support gem. When I tried this I got a message on my skill saying "support can't be socketed" however it gives me the ability to socket it. I then tested the skill to see if the curse and support gem would work at the same time and it worked. I hope this is an intended effect but the fact I get the message saying it doesn't work, but it does in fact work is a bug.