bow and a jeweller's Orbs

Bought a windripper bow yesterday with nice stats.
Tried to use a jewellers orbs to it to add extra slots.
Game writes that the socket limit is reached but the bow has only 4 sockets.
Is it a bug or some bows have less max sockets number?

Hover mouse over item, press alt, read itemlevel. Needs to be high enough for 6 sockets.

Maybe your bow is the result of some low level character turning in div cards.

Ok, so lvl should be more than 50.
Thanks for the reply