diff --git a/core/src/com/unciv/logic/BackwardCompatibility.kt b/core/src/com/unciv/logic/BackwardCompatibility.kt
index a92d1644b7..de0f5f96d6 100644
--- a/core/src/com/unciv/logic/BackwardCompatibility.kt
+++ b/core/src/com/unciv/logic/BackwardCompatibility.kt
@@ -30,6 +30,7 @@ object BackwardCompatibility {
 
         // Mod decided you can't repair things anymore - get rid of old pillaged improvements
         removeOldPillagedImprovements()
+        removeMissingLastSeenImprovements()
 
         handleMissingReferencesForEachCity()
 
@@ -69,6 +70,13 @@ object BackwardCompatibility {
             }
     }
 
+    private fun GameInfo.removeMissingLastSeenImprovements() {
+        for (civ in civilizations)
+            for ((vector,improvementName) in civ.lastSeenImprovement.toList())
+                if (!ruleset.tileImprovements.containsKey(improvementName))
+                    civ.lastSeenImprovement.remove(vector)
+    }
+
     private fun GameInfo.handleMissingReferencesForEachCity() {
         for (city in civilizations.asSequence().flatMap { it.cities.asSequence() }) {