Index: ps/trunk/binaries/data/mods/public/simulation/ai/common-api/gamestate.js
===================================================================
--- ps/trunk/binaries/data/mods/public/simulation/ai/common-api/gamestate.js
+++ ps/trunk/binaries/data/mods/public/simulation/ai/common-api/gamestate.js
@@ -810,9 +810,10 @@
  */
 m.GameState.prototype.findBuilder = function(template)
 {
+	let civ = this.getPlayerCiv();
 	for (let ent of this.getOwnUnits().values())
 	{
-		let buildable = ent.buildableEntities();
+		let buildable = ent.buildableEntities(civ);
 		if (buildable && buildable.indexOf(template) !== -1)
 			return ent;
 	}
Index: ps/trunk/binaries/data/mods/public/simulation/ai/petra/queueplanBuilding.js
===================================================================
--- ps/trunk/binaries/data/mods/public/simulation/ai/petra/queueplanBuilding.js
+++ ps/trunk/binaries/data/mods/public/simulation/ai/petra/queueplanBuilding.js
@@ -38,10 +38,16 @@
 {
 	Engine.ProfileStart("Building construction start");
 
-	// We don't care which builder we assign, since they won't actually
-	// do the building themselves - all we care about is that there is
-	// at least one unit that can start the foundation
+	// We don't care which builder we assign, since they won't actually do
+	// the building themselves - all we care about is that there is at least
+	// one unit that can start the foundation (should always be the case here).
 	let builder = gameState.findBuilder(this.type);
+	if (!builder)
+	{
+			API3.warn("petra error: builder not found when starting construction.");
+			Engine.ProfileStop();
+			return;
+	}
 
 	let pos = this.findGoodPosition(gameState);
 	if (!pos)
Index: ps/trunk/binaries/data/mods/public/simulation/components/Builder.js
===================================================================
--- ps/trunk/binaries/data/mods/public/simulation/components/Builder.js
+++ ps/trunk/binaries/data/mods/public/simulation/components/Builder.js
@@ -27,19 +27,14 @@
 Builder.prototype.GetEntitiesList = function()
 {
 	let string = this.template.Entities._string;
-
 	if (!string)
 		return [];
 
-	let cmpIdentity = Engine.QueryInterface(this.entity, IID_Identity);
-	if (cmpIdentity)
-		string = string.replace(/\{civ\}/g, cmpIdentity.GetCiv());
-
-	let entities = string.split(/\s+/);
-
 	let cmpPlayer = QueryOwnerInterface(this.entity);
 	if (!cmpPlayer)
-		return entities;
+		return [];
+
+	let entities = string.replace(/\{civ\}/g, cmpPlayer.GetCiv()).split(/\s+/);
 
 	let disabledTemplates = cmpPlayer.GetDisabledTemplates();