diff --git a/packages/net/s13n/server.js b/packages/net/s13n/server.js
index 50780e7..3ed301d 100644
--- a/packages/net/s13n/server.js
+++ b/packages/net/s13n/server.js
@@ -59,16 +59,9 @@ export class ServerSynchronizer {
         payload.push(synchronized.destroyPacket(informed));
       }
       else {
-        const id = synchronized.synchronizationId();
-        const type = idFromSynchronized(synchronized.constructor);
         const packets = synchronized.packetsFor(informed);
         for (let j = 0; j < packets.length; j++) {
-          const packet = packets[j];
-          packet.data.synchronized = {
-            id,
-            type,
-          };
-          payload.push(packet);
+          payload.push(packets[j]);
         }
       }
     }
diff --git a/packages/net/s13n/synchronized.js b/packages/net/s13n/synchronized.js
index fa7f823..35cf0eb 100644
--- a/packages/net/s13n/synchronized.js
+++ b/packages/net/s13n/synchronized.js
@@ -63,6 +63,12 @@ export function SynchronizedMixin(Superclass) {
       if (!Array.isArray(packets)) {
         packets = [packets];
       }
+      // Embed synchronization info.
+      const id = this.synchronizationId();
+      const type = idFromSynchronized(this.constructor);
+      for (let i = 0; i < packets.length; i++) {
+        packets[i].data.synchronized = {id, type};
+      }
       if (this.packetsAreIdempotent()) {
         this._idempotentPackets = packets;
       }