diff --git a/lib/pleroma/web/activity_pub/object_validators/article_note_page_validator.ex b/lib/pleroma/web/activity_pub/object_validators/article_note_page_validator.ex
index ca335bc8a..57c8d1dc0 100644
--- a/lib/pleroma/web/activity_pub/object_validators/article_note_page_validator.ex
+++ b/lib/pleroma/web/activity_pub/object_validators/article_note_page_validator.ex
@@ -65,6 +65,11 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidators.ArticleNotePageValidator do
 
   defp fix_replies(data), do: data
 
+  def fix_attachments(%{"attachment" => attachment} = data) when is_map(attachment),
+    do: Map.put(data, "attachment", [attachment])
+
+  def fix_attachments(data), do: data
+
   defp fix(data) do
     data
     |> CommonFixes.fix_actor()
@@ -72,6 +77,7 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidators.ArticleNotePageValidator do
     |> fix_url()
     |> fix_tag()
     |> fix_replies()
+    |> fix_attachments()
     |> Transmogrifier.fix_emoji()
     |> Transmogrifier.fix_content_map()
   end
diff --git a/lib/pleroma/web/activity_pub/object_validators/attachment_validator.ex b/lib/pleroma/web/activity_pub/object_validators/attachment_validator.ex
index 8b641d88d..cf6e407e0 100644
--- a/lib/pleroma/web/activity_pub/object_validators/attachment_validator.ex
+++ b/lib/pleroma/web/activity_pub/object_validators/attachment_validator.ex
@@ -59,7 +59,7 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidators.AttachmentValidator do
   end
 
   def fix_media_type(data) do
-    Map.put_new(data, "mediaType", data["mimeType"])
+    Map.put_new(data, "mediaType", data["mimeType"] || "application/octet-stream")
   end
 
   defp handle_href(href, mediaType, data) do
diff --git a/test/fixtures/owncast-note-with-attachment.json b/test/fixtures/owncast-note-with-attachment.json
new file mode 100644
index 000000000..68cb6bbf7
--- /dev/null
+++ b/test/fixtures/owncast-note-with-attachment.json
@@ -0,0 +1,31 @@
+{
+  "attachment": {
+    "content": "Live stream preview",
+    "type": "Image",
+    "url": "https://owncast.localhost.localdomain/preview.gif?us=KjfNX387gm"
+  },
+  "attributedTo": "https://owncast.localhost.localdomain/federation/user/streamer",
+  "audience": "https://www.w3.org/ns/activitystreams#Public",
+  "content": "<p>I've gone live!</p><p></p><p><a class=\"hashtag\" href=\"https://directory.owncast.online/tags/owncast\">#owncast</a> <a class=\"hashtag\" href=\"https://directory.owncast.online/tags/streaming\">#streaming</a></p><a href=\"https://owncast.localhost.localdomain\">https://owncast.localhost.localdomain</a>",
+  "id": "https://owncast.localhost.localdomain/federation/KjBNuq8ng",
+  "published": "2022-04-17T15:42:03Z",
+  "tag": [
+    {
+      "href": "https://directory.owncast.online/tags/owncast",
+      "name": "#owncast",
+      "type": "Hashtag"
+    },
+    {
+      "href": "https://directory.owncast.online/tags/streaming",
+      "name": "#streaming",
+      "type": "Hashtag"
+    },
+    {
+      "href": "https://directory.owncast.online/tags/owncast",
+      "name": "#owncast",
+      "type": "Hashtag"
+    }
+  ],
+  "to": "https://www.w3.org/ns/activitystreams#Public",
+  "type": "Note"
+}
diff --git a/test/pleroma/web/activity_pub/object_validators/article_note_page_validator_test.exs b/test/pleroma/web/activity_pub/object_validators/article_note_page_validator_test.exs
index f93537ed8..e59bf6787 100644
--- a/test/pleroma/web/activity_pub/object_validators/article_note_page_validator_test.exs
+++ b/test/pleroma/web/activity_pub/object_validators/article_note_page_validator_test.exs
@@ -43,4 +43,15 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidators.ArticleNotePageValidatorTest
 
     %{valid?: true} = ArticleNotePageValidator.cast_and_validate(note)
   end
+
+  test "a note with an attachment should work", _ do
+    insert(:user, %{ap_id: "https://owncast.localhost.localdomain/federation/user/streamer"})
+
+    note =
+      "test/fixtures/owncast-note-with-attachment.json"
+      |> File.read!()
+      |> Jason.decode!()
+
+    %{valid?: true} = ArticleNotePageValidator.cast_and_validate(note)
+  end
 end