diff --git a/nebkor-maelstrom/src/lib.rs b/nebkor-maelstrom/src/lib.rs
index 7f048b4..a4dded8 100644
--- a/nebkor-maelstrom/src/lib.rs
+++ b/nebkor-maelstrom/src/lib.rs
@@ -32,6 +32,7 @@ pub struct Runner {
     backdoor: OnceLock<Sender<Message>>,
     promises: Arc<Mutex<HashMap<u64, Sender<Message>>>>,
     outbound_tx: OnceLock<Sender<Message>>,
+    msg_id: AtomicU64,
 }
 
 impl Runner {
@@ -44,6 +45,7 @@ impl Runner {
             backdoor: OnceLock::new(),
             outbound_tx: OnceLock::new(),
             promises: Default::default(),
+            msg_id: AtomicU64::new(1),
         }
     }
 
@@ -80,11 +82,11 @@ impl Runner {
     }
 
     pub fn next_msg_id(&self) -> u64 {
-        MSG_ID.fetch_add(1, Ordering::SeqCst)
+        self.msg_id.fetch_add(1, Ordering::SeqCst)
     }
 
     pub fn cur_msg_id(&self) -> u64 {
-        MSG_ID.load(Ordering::SeqCst)
+        self.msg_id.load(Ordering::SeqCst)
     }
 
     pub fn nodes(&self) -> &[String] {
@@ -100,28 +102,12 @@ impl Runner {
     }
 
     pub fn send(&self, dest: &str, body: Body) {
-        let mut body = body;
-        if body.msg_id == 0 {
-            body.msg_id = self.next_msg_id();
-        }
-        let msg = Message {
-            src: self.node_id().to_string(),
-            dest: dest.to_string(),
-            body,
-        };
+        let msg = self.mk_msg(dest, body);
         self.outbound_tx.get().unwrap().send(msg).unwrap();
     }
 
     pub fn rpc(&self, dest: &str, body: Body) -> RpcPromise {
-        let mut body = body;
-        if body.msg_id == 0 {
-            body.msg_id = self.next_msg_id();
-        }
-        let msg = Message {
-            src: self.node_id().to_string(),
-            dest: dest.to_string(),
-            body,
-        };
+        let msg = self.mk_msg(dest, body);
         let (tx, rx) = channel();
         {
             let msg_id = msg.body.msg_id;
@@ -197,6 +183,18 @@ impl Runner {
             }
         });
     }
+
+    fn mk_msg(&self, dest: &str, body: Body) -> Message {
+        let mut body = body;
+        if body.msg_id == 0 {
+            body.msg_id = self.next_msg_id();
+        }
+        Message {
+            src: self.node_id().to_string(),
+            dest: dest.to_string(),
+            body,
+        }
+    }
 }
 
 pub fn check_err(msg: &Message) -> RpcResult {
@@ -213,5 +211,3 @@ pub fn mk_payload(payload: &[(&str, Value)]) -> Payload {
         .map(|p| (p.0.to_string(), p.1.clone()))
         .collect()
 }
-
-static MSG_ID: AtomicU64 = AtomicU64::new(0);