diff --git a/pgcommitfest/commitfest/ajax.py b/pgcommitfest/commitfest/ajax.py
index 8137dfdf..1c30ad0b 100644
--- a/pgcommitfest/commitfest/ajax.py
+++ b/pgcommitfest/commitfest/ajax.py
@@ -195,7 +195,7 @@ def parse_and_add_attachments(threadinfo, mailthread):
             # One or more attachments. For now, we're only actually going
             # to store and process the first one, even though the API gets
             # us all of them.
-            MailThreadAttachment.objects.get_or_create(
+            MailThreadAttachment.objects.update_or_create(
                 mailthread=mailthread,
                 messageid=t["msgid"],
                 defaults={
diff --git a/pgcommitfest/commitfest/tests/test_refresh_thread.py b/pgcommitfest/commitfest/tests/test_refresh_thread.py
index 55d22a22..3ebeeaa5 100644
--- a/pgcommitfest/commitfest/tests/test_refresh_thread.py
+++ b/pgcommitfest/commitfest/tests/test_refresh_thread.py
@@ -4,13 +4,13 @@
 import pytest
 
 from pgcommitfest.commitfest.ajax import refresh_single_thread
-from pgcommitfest.commitfest.models import MailThread, Patch
+from pgcommitfest.commitfest.models import MailThread, MailThreadAttachment, Patch
 
 pytestmark = pytest.mark.django_db
 
 
-def test_refresh_single_thread_updates_patch_lastmail():
-    """Regression test: patch.lastmail should get the new date, not the old one."""
+def test_refresh_single_thread():
+    """A new mail updates patch.lastmail and refreshes stale attachment info."""
     old_date = datetime(2024, 1, 1)
     new_date = datetime(2024, 6, 15)
 
@@ -26,6 +26,14 @@ def test_refresh_single_thread_updates_patch_lastmail():
     )
     p = Patch.objects.create(name="Test Patch", lastmail=old_date)
     p.mailthread_set.add(thread)
+    attachment = MailThreadAttachment.objects.create(
+        mailthread=thread,
+        messageid="old@example.com",
+        attachmentid=1,
+        filename="old.patch",
+        date=old_date,
+        author="a",
+    )
 
     api_response = [
         {
@@ -33,7 +41,8 @@ def test_refresh_single_thread_updates_patch_lastmail():
             "date": old_date,
             "from": "a",
             "subj": "T",
-            "atts": [],
+            # The archives assigned a new id to the same attachment
+            "atts": [{"id": 2, "name": "new.patch"}],
         },
         {
             "msgid": "new@example.com",
@@ -49,3 +58,6 @@ def test_refresh_single_thread_updates_patch_lastmail():
 
     p.refresh_from_db()
     assert p.lastmail == new_date
+    attachment.refresh_from_db()
+    assert (attachment.attachmentid, attachment.filename) == (2, "new.patch")
+    assert MailThreadAttachment.objects.filter(mailthread=thread).count() == 1