diff --git a/zerver/migrations/0021_migrate_attachment_data.py b/zerver/migrations/0021_migrate_attachment_data.py
index 681806816a8aa6..6761e445db2109 100644
--- a/zerver/migrations/0021_migrate_attachment_data.py
+++ b/zerver/migrations/0021_migrate_attachment_data.py
@@ -1,12 +1,36 @@
 # -*- coding: utf-8 -*-
 from __future__ import unicode_literals
 
+import os
+import glob
+
 from django.db import models, migrations
 from django.db.backends.postgresql_psycopg2.schema import DatabaseSchemaEditor
 from django.db.migrations.state import StateApps
 from django.conf import settings
 
+from boto.s3.connection import S3Connection
+
 from zerver.models import Recipient
+from zerver.lib.upload import get_bucket
+
+def get_all_local_path_ids():
+    base_path = os.path.join(settings.LOCAL_UPLOADS_DIR, 'files')
+    paths = glob.glob(base_path + '/*/*/*/*')
+    path_ids = [path.replace(base_path + '/', '') for path in paths]
+    return path_ids
+
+def get_all_s3_path_ids():
+    conn = S3Connection(settings.S3_KEY, settings.S3_SECRET_KEY)
+    bucket_name = settings.S3_AUTH_UPLOADS_BUCKET
+    bucket = get_bucket(conn, bucket_name)
+    return [key.name for key in list(bucket.list())]
+
+def get_all_path_ids():
+    if settings.LOCAL_UPLOADS_DIR is not None:
+        return get_all_local_path_ids()
+    else:
+        return get_all_s3_path_ids()
 
 def migrate_existing_data(apps, schema_editor):
     # type: (StateApps, DatabaseSchemaEditor) -> None
@@ -14,6 +38,7 @@ def migrate_existing_data(apps, schema_editor):
     Stream = apps.get_model('zerver', 'Stream')
 
     attachments = Attachment.objects.all()
+    remaining_files = get_all_path_ids()
     for entry in attachments:
         owner = entry.owner
         entry.realm = owner.realm
@@ -25,6 +50,11 @@ def migrate_existing_data(apps, schema_editor):
                     entry.is_realm_public = entry.is_realm_public or is_realm_public
 
         entry.save()
+        remaining_files.remove(entry.path_id)
+
+    for path_id in remaining_files:
+        file_name = path_id.split('/')[-1]
+        Attachment.objects.create(file_name=file_name, path_id=path_id, is_realm_public=True)
 
 class Migration(migrations.Migration):