My imagination, bug, or uncommon rule?

[sirpupnyc]

Twice in a Pokerroom 22 last night I saw situations where an all-in that wasn't a technical full raise got reraised all-in. Am I imagining that this isn't kosher by the usual rules?

For example, I bet 100, player B raises to 200, player C goes all-in for 215, I call, B goes all-in.

C would have had to raise to 300 or more for it to be raiseable, right?

Clearly this doesn't apply on Pokerroom (or it's a bug), but I'm not imagining the rule, am I?

(I was probably calling in my example above anyway, but if I'd known the action wasn't closed I might have at least given it some more thought.)