diff --git a/binaries/data/mods/public/simulation/ai/petra/gameTypeManager.js b/binaries/data/mods/public/simulation/ai/petra/gameTypeManager.js
index 987840afd8..31f65887c9 100644
--- a/binaries/data/mods/public/simulation/ai/petra/gameTypeManager.js
+++ b/binaries/data/mods/public/simulation/ai/petra/gameTypeManager.js
@@ -269,7 +269,7 @@ m.GameTypeManager.prototype.removeGuardsFromCriticalEnt = function(gameState, cr
 		if (guardEnt.getMetadata(PlayerID, "guardedEnt"))
 			guardEnt.setMetadata(PlayerID, "guardedEnt", undefined);
 	}
-	this.criticalEnts.delete(evt.entity);
+	this.criticalEnts.delete(criticalEntId);
 };
 
 m.GameTypeManager.prototype.buildWonder = function(gameState, queues)