Nature's Swiftness

Nature's Swiftness

Activation gives casting free spell... and if i for example cast lighting bolt and while its in midflight i activate natures swiftness to pop instant chain lighting, bolt thats in mid air wastes natures swiftness, and not Chain lighting i planed.
Natural swiftness buff should perish after casting finished and spell landed, and not when any spell lands (even though you activated NS while that spell was flying)