diff --git a/src/core/errors.ts b/src/core/errors.ts
index 241e441c..1f48ddae 100644
--- a/src/core/errors.ts
+++ b/src/core/errors.ts
@@ -4,6 +4,16 @@ import * as Ably from 'ably';
  * Error codes for the Chat SDK.
  */
 export enum ErrorCodes {
+  /**
+   * The message was rejected before publishing by a rule on the chat room.
+   */
+  MessageRejectedByBeforePublishRule = 42211,
+
+  /**
+   * The message was rejected before publishing by a moderation rule on the chat room.
+   */
+  MessageRejectedByModeration = 42213,
+
   /**
    * The messages feature failed to attach.
    */