diff --git a/keyserver/src/creators/thread-creator.js b/keyserver/src/creators/thread-creator.js
--- a/keyserver/src/creators/thread-creator.js
+++ b/keyserver/src/creators/thread-creator.js
@@ -444,6 +444,7 @@
         creatorID: viewer.userID,
         time,
         sourceMessage: editedSourceMessage,
+        targetMessageID: editedSourceMessage.id,
       },
       {
         type: messageTypes.CREATE_SIDEBAR,
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
@@ -128,7 +128,14 @@
     id: ?string,
   ): RawSidebarSourceMessageInfo {
     invariant(id, 'RawSidebarSourceMessageInfo needs id');
-    return { ...messageData, id };
+    return {
+      creatorID: messageData.creatorID,
+      sourceMessage: messageData.sourceMessage,
+      threadID: messageData.threadID,
+      time: messageData.time,
+      type: messageData.type,
+      id,
+    };
   },
 
   shimUnsupportedMessageInfo(
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
@@ -232,7 +232,7 @@
 // Raw*MessageInfo = used by server, and contained in client's local store
 // *MessageInfo = used by client in UI code
 
-export type SidebarSourceMessageData = {
+type SidebarSourceSharedBase = {
   +type: 17,
   +threadID: string,
   +creatorID: string,
@@ -240,6 +240,11 @@
   +sourceMessage?: RawComposableMessageInfo | RawRobotextMessageInfo,
 };
 
+export type SidebarSourceMessageData = {
+  ...SidebarSourceSharedBase,
+  +targetMessageID?: string,
+};
+
 export type MessageData =
   | TextMessageData
   | CreateThreadMessageData
@@ -290,7 +295,7 @@
   | RawUnsupportedMessageInfo
   | RawTogglePinMessageInfo;
 export type RawSidebarSourceMessageInfo = {
-  ...SidebarSourceMessageData,
+  ...SidebarSourceSharedBase,
   id: string,
 };