diff --git a/keyserver/src/fetchers/message-fetchers.js b/keyserver/src/fetchers/message-fetchers.js
--- a/keyserver/src/fetchers/message-fetchers.js
+++ b/keyserver/src/fetchers/message-fetchers.js
@@ -24,6 +24,7 @@
   defaultMaxMessageAge,
   type FetchPinnedMessagesRequest,
   type FetchPinnedMessagesResult,
+  isMessageSidebarSourceReactionOrEdit,
 } from 'lib/types/message-types.js';
 import { threadPermissions } from 'lib/types/thread-types.js';
 import { ServerError } from 'lib/utils/errors.js';
@@ -744,13 +745,12 @@
 
   for (const message of messages) {
     let { rawMessageInfo } = message;
+    invariant(
+      !isMessageSidebarSourceReactionOrEdit(rawMessageInfo),
+      'SIDEBAR_SOURCE or TOGGLE_PIN should not point to a ' +
+        'SIDEBAR_SOURCE, REACTION or EDIT_MESSAGE',
+    );
     if (rawMessageInfo.id) {
-      invariant(
-        rawMessageInfo.type !== messageTypes.SIDEBAR_SOURCE &&
-          rawMessageInfo.type !== messageTypes.REACTION &&
-          rawMessageInfo.type !== messageTypes.EDIT_MESSAGE,
-        'SIDEBAR_SOURCE should not point to a SIDEBAR_SOURCE, REACTION or EDIT_MESSAGE',
-      );
       const editedContent = edits.get(rawMessageInfo.id);
       if (editedContent && rawMessageInfo.type === messageTypes.TEXT) {
         rawMessageInfo = {
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
@@ -10,13 +10,14 @@
 } from './message-spec.js';
 import { joinResult } from './utils.js';
 import type { PlatformDetails } from '../../types/device-types.js';
-import type {
-  RawSidebarSourceMessageInfo,
-  SidebarSourceMessageData,
-  SidebarSourceMessageInfo,
-  ClientDBMessageInfo,
+import {
+  type RawSidebarSourceMessageInfo,
+  type SidebarSourceMessageData,
+  type SidebarSourceMessageInfo,
+  type ClientDBMessageInfo,
+  messageTypes,
+  isMessageSidebarSourceReactionOrEdit,
 } from '../../types/message-types.js';
-import { messageTypes } 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';
@@ -106,10 +107,7 @@
       rawMessageInfo.sourceMessage,
     );
     invariant(
-      sourceMessage &&
-        sourceMessage.type !== messageTypes.SIDEBAR_SOURCE &&
-        sourceMessage.type !== messageTypes.REACTION &&
-        sourceMessage.type !== messageTypes.EDIT_MESSAGE,
+      sourceMessage && !isMessageSidebarSourceReactionOrEdit(sourceMessage),
       'Sidebars can not be created from SIDEBAR SOURCE, REACTION or EDIT MESSAGE',
     );
 
diff --git a/lib/types/message-types.js b/lib/types/message-types.js
--- a/lib/types/message-types.js
+++ b/lib/types/message-types.js
@@ -214,6 +214,16 @@
   return messageData.localID;
 }
 
+export function isMessageSidebarSourceReactionOrEdit(
+  message: RawMessageInfo | MessageInfo,
+): boolean %checks {
+  return (
+    message.type === messageTypes.SIDEBAR_SOURCE ||
+    message.type === messageTypes.REACTION ||
+    message.type === messageTypes.EDIT_MESSAGE
+  );
+}
+
 const mediaMessageTypes = new Set([
   messageTypes.IMAGES,
   messageTypes.MULTIMEDIA,