diff --git a/lib/shared/messages/sidebar-source-message-spec.js b/lib/shared/messages/sidebar-source-message-spec.js
--- a/lib/shared/messages/sidebar-source-message-spec.js
+++ b/lib/shared/messages/sidebar-source-message-spec.js
@@ -17,7 +17,6 @@
   type ClientDBMessageInfo,
   rawSidebarSourceMessageInfoValidator,
 } from '../../types/message-types.js';
-import type { RawUnsupportedMessageInfo } from '../../types/messages/unsupported.js';
 import type { NotifTexts } from '../../types/notif-types.js';
 import type { RelativeUserInfo } from '../../types/user-types.js';
 import { isInvalidSidebarSource } from '../message-utils.js';
@@ -131,32 +130,6 @@
     return { ...messageData, id };
   },
 
-  shimUnsupportedMessageInfo(
-    rawMessageInfo: RawSidebarSourceMessageInfo,
-  ): RawSidebarSourceMessageInfo | RawUnsupportedMessageInfo {
-    if (rawMessageInfo.sourceMessage) {
-      return rawMessageInfo;
-    }
-    const { id } = rawMessageInfo;
-    invariant(id !== null && id !== undefined, 'id should be set on server');
-    return {
-      type: messageTypes.UNSUPPORTED,
-      id,
-      threadID: rawMessageInfo.threadID,
-      creatorID: rawMessageInfo.creatorID,
-      time: rawMessageInfo.time,
-      robotext: 'first message in thread',
-      dontPrefixCreator: true,
-      unsupportedMessageInfo: rawMessageInfo,
-    };
-  },
-
-  unshimMessageInfo(
-    unwrapped: RawSidebarSourceMessageInfo,
-  ): RawSidebarSourceMessageInfo {
-    return unwrapped;
-  },
-
   notificationTexts(): Promise<NotifTexts> {
     invariant(
       false,