diff --git a/core/src/com/unciv/logic/trade/TradeLogic.kt b/core/src/com/unciv/logic/trade/TradeLogic.kt
index 4d396c4706..5aa7d7622f 100644
--- a/core/src/com/unciv/logic/trade/TradeLogic.kt
+++ b/core/src/com/unciv/logic/trade/TradeLogic.kt
@@ -97,7 +97,7 @@ class TradeLogic(val ourCivilization:CivilizationInfo, val otherCivilization: Ci
                 if (offer.type == TradeType.City) {
                     val city = from.cities.first { it.id == offer.name }
                     city.moveToCiv(to)
-                    city.getCenterTile().getUnits().forEach { it.movement.teleportToClosestMoveableTile() }
+                    city.getCenterTile().getUnits().toList().forEach { it.movement.teleportToClosestMoveableTile() }
                     to.updateViewableTiles()
                     from.updateViewableTiles()
                 }