diff --git a/keyserver/src/responders/message-responders.js b/keyserver/src/responders/message-responders.js
--- a/keyserver/src/responders/message-responders.js
+++ b/keyserver/src/responders/message-responders.js
@@ -41,6 +41,7 @@
 import {
   assignMedia,
   assignMessageContainerToMedia,
+  assignThreadToMedia,
 } from '../updaters/upload-updaters';
 import { validateInput } from '../utils/validation-utils';
 
@@ -184,6 +185,8 @@
     );
   }
 
+  await assignThreadToMedia(viewer);
+
   return { newMessageInfo };
 }
 
diff --git a/keyserver/src/updaters/upload-updaters.js b/keyserver/src/updaters/upload-updaters.js
--- a/keyserver/src/updaters/upload-updaters.js
+++ b/keyserver/src/updaters/upload-updaters.js
@@ -35,4 +35,16 @@
   await dbQuery(query);
 }
 
-export { assignMedia, assignMessageContainerToMedia };
+async function assignThreadToMedia(viewer: Viewer): Promise<void> {
+  const query = SQL`
+    UPDATE uploads 
+    SET thread = (
+      SELECT thread FROM messages 
+      WHERE messages.id = uploads.container
+    )
+    WHERE uploader = ${viewer.id} AND thread IS NULL
+  `;
+  await dbQuery(query);
+}
+
+export { assignMedia, assignMessageContainerToMedia, assignThreadToMedia };