diff --git a/game/modules/tome/class/NPC.lua b/game/modules/tome/class/NPC.lua
index d05ef9d823c823d4ad21a9a6c3e132b8b1a299f7..25f59ab1151d23582ecb8624655ca74c8fe8e82b 100644
--- a/game/modules/tome/class/NPC.lua
+++ b/game/modules/tome/class/NPC.lua
@@ -183,7 +183,7 @@ function _M:seen_by(who)
 		end
 		return
 	end
-	if who.ai_state and who.ai_state.target_last_seen then
+	if who.ai_state and who.ai_state.target_last_seen and type(who.ai_state.target_last_seen) == "table" then
 		-- Don't believe allies if they saw the target far, far away
 		if who.ai_state.target_last_seen.x and who.ai_state.target_last_seen.y and core.fov.distance(self.x, self.y, who.ai_state.target_last_seen.x, who.ai_state.target_last_seen.y) > self.sight then return end
 		-- Don't believe allies if they saw the target over 10 turns ago