diff --git a/core/src/mindustry/ai/WaveSpawner.java b/core/src/mindustry/ai/WaveSpawner.java
index e8f52f9a81..1c6d46d6d5 100644
--- a/core/src/mindustry/ai/WaveSpawner.java
+++ b/core/src/mindustry/ai/WaveSpawner.java
@@ -23,13 +23,18 @@ public class WaveSpawner{
     private static final float margin = 0f, coreMargin = tilesize * 2f, maxSteps = 30;
 
     private int tmpCount;
-    private Seq<Tile> spawns = new Seq<>();
+    private Seq<Tile> spawns = new Seq<>(false);
     private boolean spawning = false;
     private boolean any = false;
     private Tile firstSpawn = null;
 
     public WaveSpawner(){
         Events.on(WorldLoadEvent.class, e -> reset());
+
+        Events.on(TileOverlayChangeEvent.class, e -> {
+            if(e.previous == Blocks.spawn) spawns.remove(e.tile);
+            if(e.overlay == Blocks.spawn) spawns.add(e.tile);
+        });
     }
 
     @Nullable
diff --git a/core/src/mindustry/game/EventType.java b/core/src/mindustry/game/EventType.java
index 84e6ae3afa..e9f58c038c 100644
--- a/core/src/mindustry/game/EventType.java
+++ b/core/src/mindustry/game/EventType.java
@@ -414,6 +414,22 @@ public class EventType{
         }
     }
 
+    /**
+     * Called when a tile changes its overlay. Do not cache or use with a timer.
+     * Do not modify any tiles inside listener code.
+     * */
+    public static class TileOverlayChangeEvent{
+        public Tile tile;
+        public Floor previous, overlay;
+
+        public TileOverlayChangeEvent set(Tile tile, Floor previous, Floor overlay){
+            this.tile = tile;
+            this.previous = previous;
+            this.overlay = overlay;
+            return this;
+        }
+    }
+
     /**
      * Called after a building's team changes.
      * Event object is reused, do not nest!
diff --git a/core/src/mindustry/world/Tile.java b/core/src/mindustry/world/Tile.java
index 0a14cc438e..45f8ecfa93 100644
--- a/core/src/mindustry/world/Tile.java
+++ b/core/src/mindustry/world/Tile.java
@@ -24,6 +24,7 @@ public class Tile implements Position, QuadTreeObject, Displayable{
     private static final TileChangeEvent tileChange = new TileChangeEvent();
     private static final TilePreChangeEvent preChange = new TilePreChangeEvent();
     private static final TileFloorChangeEvent floorChange = new TileFloorChangeEvent();
+    private static final TileOverlayChangeEvent overlayChange = new TileOverlayChangeEvent();;
     private static final ObjectSet<Building> tileSet = new ObjectSet<>();
 
     /**
@@ -408,9 +409,16 @@ public class Tile implements Position, QuadTreeObject, Displayable{
     public void setOverlay(Block block){
         if(this.overlay == block) return;
 
+        var prev = this.overlay;
+
         this.overlay = (Floor)block;
 
         recache();
+
+        if(!world.isGenerating()){
+            Events.fire(overlayChange.set(this, prev, this.overlay));
+        }
+
         if(!world.isGenerating() && build != null){
             build.onProximityUpdate();
         }
diff --git a/gradle.properties b/gradle.properties
index d429869111..60c1e38211 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -26,4 +26,4 @@ org.gradle.caching=true
 org.gradle.internal.http.socketTimeout=100000
 org.gradle.internal.http.connectionTimeout=100000
 android.enableR8.fullMode=false
-archash=82df0d1a93
+archash=071fdffaf2