diff --git a/core/src/mindustry/io/JsonIO.java b/core/src/mindustry/io/JsonIO.java
index 8263dae6c5..b89f013b0c 100644
--- a/core/src/mindustry/io/JsonIO.java
+++ b/core/src/mindustry/io/JsonIO.java
@@ -308,7 +308,10 @@ public class JsonIO{
                 int i = 0;
                 for(var value = data.child; value != null; value = value.next, i++){
                     for(var parent = value.get("parents").child; parent != null; parent = parent.next){
-                        exec.all.get(i).parents.add(exec.all.get(parent.asInt()));
+                        int val = parent.asInt();
+                        if(val >= 0 && val < exec.all.size){
+                            exec.all.get(i).parents.add(exec.all.get(val));
+                        }
                     }
                 }
 
diff --git a/core/src/mindustry/maps/Map.java b/core/src/mindustry/maps/Map.java
index 0abe2aaffa..8bbaee5748 100644
--- a/core/src/mindustry/maps/Map.java
+++ b/core/src/mindustry/maps/Map.java
@@ -105,7 +105,7 @@ public class Map implements Comparable<Map>, Publishable{
             return result;
         }catch(Exception e){
             //error reading rules. ignore?
-            e.printStackTrace();
+            Log.err(e);
             return new Rules();
         }
     }