diff --git a/keyserver/src/push/send.js b/keyserver/src/push/send.js
--- a/keyserver/src/push/send.js
+++ b/keyserver/src/push/send.js
@@ -467,7 +467,7 @@
   collapseKey: ?string,
   badgeOnly: boolean,
   unreadCount: number,
-  codeVersion: ?number,
+  codeVersion: number,
 ): apn.Notification {
   const uniqueID = uuidv4();
   const notification = new apn.Notification();
@@ -493,6 +493,9 @@
   notification.payload.id = uniqueID;
   notification.payload.threadID = threadInfo.id;
   notification.payload.messageInfos = JSON.stringify(newRawMessageInfos);
+  if (codeVersion > 1000) {
+    notification.mutableContent = true;
+  }
   if (collapseKey) {
     notification.collapseId = collapseKey;
   }