Neil Critchley's team went into Monday's fixture ahead of their hosts by virtue of goals scored but surrendered their place at the summit on an evening to forget.
The Foxes took just two minutes to go ahead as Harvey Barnes reacted quickest after Josh Gordon's deflected long-distance strike had clattered the post.
The forward still had plenty of work to do with defenders moving to close him down, but found the space to squeeze a shot beyond Kamil Grabara.
The early goal provided a platform for Leicester to dominate the remainder of the half, though they initially found themselves unable to capitalise on their ascendancy.