diff --git a/core/src/mindustry/io/MapIO.java b/core/src/mindustry/io/MapIO.java
index 8dc8088681..18f6a712bd 100644
--- a/core/src/mindustry/io/MapIO.java
+++ b/core/src/mindustry/io/MapIO.java
@@ -79,12 +79,8 @@ public class MapIO{
             CachedTile tile = new CachedTile(){
                 @Override
                 public void setBlock(Block type){
-                    //previous state.
-                    if(build != null && build.block instanceof CoreBlock){
-                        map.teams.add(build.team.id);
-                    }
-
                     super.setBlock(type);
+
                     int c = colorFor(block(), Blocks.air, Blocks.air, team());
                     if(c != black){
                         walls.draw(x, floors.getHeight() - 1 - y, c);
@@ -104,6 +100,27 @@ public class MapIO{
                     world.setGenerating(false);
                 }
 
+                @Override
+                public void onReadBuilding(){
+                    //read team colors
+                    if(tile.build != null){
+                        int c = tile.build.team.color.rgba8888();
+                        int size = tile.block().size;
+                        int offsetx = -(size - 1) / 2;
+                        int offsety = -(size - 1) / 2;
+                        for(int dx = 0; dx < size; dx++){
+                            for(int dy = 0; dy < size; dy++){
+                                int drawx = tile.x + dx + offsetx, drawy = tile.y + dy + offsety;
+                                walls.draw(drawx, floors.getHeight() - 1 - drawy, c);
+                            }
+                        }
+
+                        if(tile.build.block instanceof CoreBlock){
+                            map.teams.add(tile.build.team.id);
+                        }
+                    }
+                }
+
                 @Override
                 public Tile tile(int index){
                     tile.x = (short)(index % map.width);
diff --git a/core/src/mindustry/io/SaveVersion.java b/core/src/mindustry/io/SaveVersion.java
index ab243b0823..76e3b1cc5c 100644
--- a/core/src/mindustry/io/SaveVersion.java
+++ b/core/src/mindustry/io/SaveVersion.java
@@ -263,6 +263,8 @@ public abstract class SaveVersion extends SaveFileReader{
                             //skip the entity region, as the entity and its IO code are now gone
                             skipChunk(stream, true);
                         }
+
+                        context.onReadBuilding();
                     }
                 }else if(hadData){
                     tile.setBlock(block);
diff --git a/core/src/mindustry/io/legacy/LegacySaveVersion.java b/core/src/mindustry/io/legacy/LegacySaveVersion.java
index a511868356..f533ebd27d 100644
--- a/core/src/mindustry/io/legacy/LegacySaveVersion.java
+++ b/core/src/mindustry/io/legacy/LegacySaveVersion.java
@@ -85,6 +85,8 @@ public abstract class LegacySaveVersion extends SaveVersion{
                     }catch(Throwable e){
                         throw new IOException("Failed to read tile entity of block: " + block, e);
                     }
+
+                    context.onReadBuilding();
                 }else{
                     int consecutives = stream.readUnsignedByte();
 
diff --git a/core/src/mindustry/maps/Map.java b/core/src/mindustry/maps/Map.java
index 0bed8f0408..1f9ab65cdd 100644
--- a/core/src/mindustry/maps/Map.java
+++ b/core/src/mindustry/maps/Map.java
@@ -70,7 +70,7 @@ public class Map implements Comparable<Map>, Publishable{
     }
 
     public Fi previewFile(){
-        return Vars.mapPreviewDirectory.child((workshop ? file.parent().name() : file.nameWithoutExtension()) + ".png");
+        return Vars.mapPreviewDirectory.child((workshop ? file.parent().name() : file.nameWithoutExtension()) + "_v2.png");
     }
 
     public Fi cacheFile(){
diff --git a/core/src/mindustry/world/WorldContext.java b/core/src/mindustry/world/WorldContext.java
index 760aa0938f..498e4e587b 100644
--- a/core/src/mindustry/world/WorldContext.java
+++ b/core/src/mindustry/world/WorldContext.java
@@ -20,4 +20,7 @@ public interface WorldContext{
     /** End generating, prepares tiles.*/
     void end();
 
+    /** Called when a building is finished reading. */
+    default void onReadBuilding(){}
+
 }