Sleeping shotgun guy in MAP02 (Doom II)

In MAP02 of Doom II, after opening the pillar to the left of the starting point and past the doors requiring the blue key (Co-ordinates: 946,903,-16), there is a shotgun guy next to a barrel. However, he ignores the player and does not "wake up" as monsters usually do when spotting a player.

Usually, the bug is not noticed, as the player must confront two troopers before reaching the sergeant. The action of killing them usually wakes up the sergeant (who is still sensitive to sound).

Technical
The behavior occurs due to a bug in Doom's line of sight code. The code which causes it is located in p_sight.c, in the function P_DivlineSide.