Switch bounce vs LC Spike Voltage
Now you know what a series underdamped 2nd order effect looks like. 

2nd order because there are at least 2 dominant reactive parts, L &amp; C where the inductance and capacitance is probably the series wire length of your probe ground length and coaxial probe capacitance giving a sine wave around 30% of 40ns or 80MHz with a 10:1 probe.

Reduce the inductance length or adding series R to dampen the wave with Zc(f)=R would reduce the ringing.

But this as nothing to do with the question of course as I indicated in comments.