diff --git a/changelog.d/3884.fix b/changelog.d/3884.fix
new file mode 100644
index 000000000..f8dbb2bbf
--- /dev/null
+++ b/changelog.d/3884.fix
@@ -0,0 +1 @@
+Allow non-HTTP(s) URIs in "url" fields for compatibility with "FEP-fffd: Proxy Objects"
\ No newline at end of file
diff --git a/lib/pleroma/ecto_type/activity_pub/object_validators/bare_uri.ex b/lib/pleroma/ecto_type/activity_pub/object_validators/bare_uri.ex
new file mode 100644
index 000000000..1038296e7
--- /dev/null
+++ b/lib/pleroma/ecto_type/activity_pub/object_validators/bare_uri.ex
@@ -0,0 +1,23 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2023 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.EctoType.ActivityPub.ObjectValidators.BareUri do
+  use Ecto.Type
+
+  def type, do: :string
+
+  def cast(uri) when is_binary(uri) do
+    case URI.parse(uri) do
+      %URI{scheme: nil} -> :error
+      %URI{} -> {:ok, uri}
+      _ -> :error
+    end
+  end
+
+  def cast(_), do: :error
+
+  def dump(data), do: {:ok, data}
+
+  def load(data), do: {:ok, data}
+end
diff --git a/lib/pleroma/web/activity_pub/object_validators/common_fields.ex b/lib/pleroma/web/activity_pub/object_validators/common_fields.ex
index 7b60c139a..d580208df 100644
--- a/lib/pleroma/web/activity_pub/object_validators/common_fields.ex
+++ b/lib/pleroma/web/activity_pub/object_validators/common_fields.ex
@@ -58,7 +58,7 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidators.CommonFields do
       field(:like_count, :integer, default: 0)
       field(:announcement_count, :integer, default: 0)
       field(:inReplyTo, ObjectValidators.ObjectID)
-      field(:url, ObjectValidators.Uri)
+      field(:url, ObjectValidators.BareUri)
 
       field(:likes, {:array, ObjectValidators.ObjectID}, default: [])
       field(:announcements, {:array, ObjectValidators.ObjectID}, default: [])
diff --git a/test/pleroma/ecto_type/activity_pub/object_validators/bare_uri_test.ex b/test/pleroma/ecto_type/activity_pub/object_validators/bare_uri_test.ex
new file mode 100644
index 000000000..226383c3c
--- /dev/null
+++ b/test/pleroma/ecto_type/activity_pub/object_validators/bare_uri_test.ex
@@ -0,0 +1,25 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2023 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.EctoType.ActivityPub.ObjectValidators.BareUriTest do
+  use Pleroma.DataCase, async: true
+
+  alias Pleroma.EctoType.ActivityPub.ObjectValidators.BareUri
+
+  test "diaspora://" do
+    text = "diaspora://alice@fediverse.example/post/deadbeefdeadbeefdeadbeefdeadbeef"
+    assert {:ok, text} = BareUri.cast(text)
+  end
+
+  test "nostr:" do
+    text = "nostr:note1gwdeadbeefdeadbeefdeadbeefdeadbeefdeadbeefdeadbeefdeadbeef"
+    assert {:ok, text} = BareUri.cast(text)
+  end
+
+  test "errors for non-URIs" do
+    assert :error == SafeText.cast(1)
+    assert :error == SafeText.cast("foo")
+    assert :error == SafeText.cast("foo bar")
+  end
+end