SN74LV165A with slow clock

My customer found a small glitch on the clock signal at 1 or 2ns after that passed 1/2 Vcc. The SN74LV165A is clocked about 1MHz but the slope is more than 100ns so the glitch peak is not far from the 1/2 Vcc point. The PCB is just single layer and he understand the power / gnd routing is weak, also the clock slope is slowed for EMI suppression. A question from customer is ; " is the glitch due to internal toggling current since it appeared only rignt after the clock passed the mid point ? "  The PCB has long traces but no other devices toggling at that timing and similar glitch waveform appread on the Vcc pin of the device. Thanks.