diff --git a/src/dorkbox/network/rmi/RemoteObjectSerializer.java b/src/dorkbox/network/rmi/RemoteObjectSerializer.java
index 4193ba65..8a73fcfb 100644
--- a/src/dorkbox/network/rmi/RemoteObjectSerializer.java
+++ b/src/dorkbox/network/rmi/RemoteObjectSerializer.java
@@ -60,7 +60,7 @@ class RemoteObjectSerializer<T> extends Serializer<T> {
         KryoExtra kryoExtra = (KryoExtra) kryo;
         int id = kryoExtra.connection.getRegisteredId(object);
         if (id == Integer.MAX_VALUE) {
-            throw new RuntimeException("Object not found in RMI objectSpace: " + object);
+            throw new IllegalStateException("Object not found in RMI objectSpace: " + object);
         }
 
         output.writeInt(id, true);