diff --git a/core/src/com/unciv/logic/city/CityInfo.kt b/core/src/com/unciv/logic/city/CityInfo.kt
index 9a2f8d8fd7..a73a9ccdd7 100644
--- a/core/src/com/unciv/logic/city/CityInfo.kt
+++ b/core/src/com/unciv/logic/city/CityInfo.kt
@@ -269,7 +269,7 @@ class CityInfo {
         }
 
         for(building in cityConstructions.getBuiltBuildings()
-                .filter{ it.uniqueTo != newCivInfo.civName && it.replaces != ""}) {
+                .filter{ it.uniqueTo != newCivInfo.civName && it.replaces != null}) {
             cityConstructions.removeBuilding(building.name)
             cityConstructions.addBuilding(building.replaces!!)
         }