[ToME 1.5.10] Rune of the Rift + Stone Wall enemy despawn

[juances]

So I rifted a guardian in Ruined Dungeon, then placed Stone Wall lvl4 on top (my idea was to trap him to get more time and maybe some suffocation damage) but apparently, if you block all adjacent tiles, the enemy just never spawns back?

And it didn't count as a kill, so I can't activate the orbs to unlock the gate on the Ruined Dungeon.

I can replicate it with any other enemy, you cast stone wall at the center of the rift to block all tiles in a radius of 1 (if you only block the rift, the enemy will spawn on any adjacent tile, so I assume there's already a safety check, can this be increased to 3 or 4 tiles?). It's not a big deal against random enemies but can screw up quests against a boss.