diff --git a/core/src/com/unciv/logic/BackwardCompatibility.kt b/core/src/com/unciv/logic/BackwardCompatibility.kt
index 48129e975b..83ab0426ec 100644
--- a/core/src/com/unciv/logic/BackwardCompatibility.kt
+++ b/core/src/com/unciv/logic/BackwardCompatibility.kt
@@ -22,14 +22,9 @@ object BackwardCompatibility {
      * This function removes them so the game doesn't crash when it tries to access them.
      */
     fun GameInfo.removeMissingModReferences() {
-        for (tile in tileMap.values) {
-            for (terrainFeature in tile.terrainFeatures.filter{ !ruleSet.terrains.containsKey(it) })
-                tile.terrainFeatures.remove(terrainFeature)
-            if (tile.resource != null && !ruleSet.tileResources.containsKey(tile.resource!!))
-                tile.resource = null
-            if (tile.improvement != null && !ruleSet.tileImprovements.containsKey(tile.improvement!!))
-                tile.improvement = null
+        tileMap.removeMissingTerrainModReferences(ruleSet)
 
+        for (tile in tileMap.values) {
             for (unit in tile.getUnits()) {
                 if (!ruleSet.units.containsKey(unit.name)) tile.removeUnit(unit)
 
diff --git a/core/src/com/unciv/logic/map/TileMap.kt b/core/src/com/unciv/logic/map/TileMap.kt
index 06c6ffec63..4ce876dfdd 100644
--- a/core/src/com/unciv/logic/map/TileMap.kt
+++ b/core/src/com/unciv/logic/map/TileMap.kt
@@ -429,6 +429,20 @@ class TileMap {
         }
     }
 
+    fun removeMissingTerrainModReferences(ruleSet: Ruleset) {
+        for (tile in this.values) {
+            for (terrainFeature in tile.terrainFeatures.filter { !ruleSet.terrains.containsKey(it) })
+                tile.terrainFeatures.remove(terrainFeature)
+            if (tile.resource != null && !ruleSet.tileResources.containsKey(tile.resource!!))
+                tile.resource = null
+            if (tile.improvement != null && !ruleSet.tileImprovements.containsKey(tile.improvement!!))
+                tile.improvement = null
+        }
+        for (startingLocation in startingLocations.toList())
+            if (startingLocation.nation !in ruleSet.nations.keys)
+                startingLocations.remove(startingLocation)
+    }
+
     /** Tries to place the [unitName] into the [TileInfo] closest to the given [position]
      * @param position where to try to place the unit (or close - max 10 tiles distance)
      * @param unitName name of the [BaseUnit][com.unciv.models.ruleset.unit.BaseUnit] to create and place
diff --git a/core/src/com/unciv/ui/mapeditor/MapEditorMenuPopup.kt b/core/src/com/unciv/ui/mapeditor/MapEditorMenuPopup.kt
index 1d33f80949..d910e652ce 100644
--- a/core/src/com/unciv/ui/mapeditor/MapEditorMenuPopup.kt
+++ b/core/src/com/unciv/ui/mapeditor/MapEditorMenuPopup.kt
@@ -169,6 +169,9 @@ class MapEditorMenuPopup(var mapEditorScreen: MapEditorScreen): Popup(mapEditorS
             ruleset.mods += mapParameters.mods
             ruleset.modOptions = newRuleset.modOptions
 
+            mapEditorScreen.tileMap.removeMissingTerrainModReferences(ruleset)
+            mapEditorScreen.mapHolder.updateTileGroups()
+
             ImageGetter.setNewRuleset(ruleset)
         }