Unable to Purchase Magus Enchantment While Playing Fiddlesticks

For some reason the Magus enchantment is disabled when I play Fiddlesticks, so I am unable to buy it. This has happened twice now, and it is really annoying. I love the fact that the ap jungle item now gives 20% cdr, but if I cannot buy it, then it makes playing Fiddlesticks less enjoyable. I would greatly appreciate it if someone could look into this matter and get back to me.