diff --git a/src/protocol/arena.rs b/src/protocol/arena.rs
index e55efe6a0da9a3f0b48378dedb3f230847a216a1..1e4b64f9ae2b6d7e47f4e24d33b1a6a1b3b7d905 100644
--- a/src/protocol/arena.rs
+++ b/src/protocol/arena.rs
@@ -1,11 +1,23 @@
+use crate::common::*;
 use core::hash::Hash;
 use core::marker::PhantomData;
 
-#[derive(Debug, serde::Serialize, serde::Deserialize)]
+#[derive(serde::Serialize, serde::Deserialize)]
 pub struct Id<T> {
     index: u32,
     _phantom: PhantomData<T>,
 }
+#[derive(Debug, serde::Serialize, serde::Deserialize)]
+pub struct Arena<T> {
+    store: Vec<T>,
+}
+//////////////////////////////////
+
+impl<T> Debug for Id<T> {
+    fn fmt(&self, f: &mut Formatter) -> std::fmt::Result {
+        f.debug_struct("Id").field("index", &self.index).finish()
+    }
+}
 impl<T> Clone for Id<T> {
     fn clone(&self) -> Self {
         *self
@@ -23,11 +35,6 @@ impl<T> Hash for Id<T> {
         self.index.hash(h);
     }
 }
-
-#[derive(Debug, serde::Serialize, serde::Deserialize)]
-pub struct Arena<T> {
-    store: Vec<T>,
-}
 impl<T> Arena<T> {
     pub fn new() -> Self {
         Self { store: vec![] }