As I explicitly set my search path prior to any of this, I don't think that's an issue. Of course, I could have simply have set it wrongly. In any case, adding ::hstore after the parameters threw a "type hstore does not exist" and enclosing the whole CONNECTOR_TIME_OUT... inside parenthesis caused the same does not exist error.
You are correct, though, Tom, that the hstore extension is 1.1. Is there some other, not =>, construct I should be using? Curiously, I just checked my personal sandbox database (9.5) and the hstore there is 1.3, but like I said earlier the update succeeds on that one.