Tahm bug?

i was playing tahm today and his w goes on cool down after i eat a minion and try to spit it out. for example i was playing a aram so as a tohm i want to try to poke so i eat a minion press w again to spit it out. now once the cool down goes down i try to do the combo again but after i inject the minion it can not spit it out until the cool down goes down ( is that secondary cool down suppose to be there?