When player gets hit when blocking with a shield and no damage is taken, if they have the Infested effect applied, they will still spawn silverfish.

How to reproduce

1. Apply yourself the Infested effect for a few minutes.
2. Summon a medium or large slime, for easier reproduction.
3. Get a shield, switch to survival and block the attacks from the slime.
4. Notice how after a few blocked hits (before the shield breaks) you spawn some silverfish.