diff --git a/lib/federation/activity_pub/transmogrifier.ex b/lib/federation/activity_pub/transmogrifier.ex
index 40c612c83..f4ed9a6be 100644
--- a/lib/federation/activity_pub/transmogrifier.ex
+++ b/lib/federation/activity_pub/transmogrifier.ex
@@ -850,8 +850,8 @@ defmodule Mobilizon.Federation.ActivityPub.Transmogrifier do
   # Handle incoming `Accept` activities wrapping a `Join` activity on an event
   defp do_handle_incoming_accept_join(join_object, %Actor{} = actor_accepting) do
     case get_participant(join_object, actor_accepting) do
-      {:ok, participant} ->
-        do_handle_incoming_accept_join_event(participant, actor_accepting)
+      {:ok, activity, participant} ->
+        do_handle_incoming_accept_join_event(participant, actor_accepting, activity)
 
       {:error, _err} ->
         case get_member(join_object) do
@@ -870,17 +870,22 @@ defmodule Mobilizon.Federation.ActivityPub.Transmogrifier do
     end
   end
 
-  defp do_handle_incoming_accept_join_event(%Participant{role: :participant}, _actor) do
+  defp do_handle_incoming_accept_join_event(
+         %Participant{role: :participant} = participant,
+         _actor,
+         activity
+       ) do
     Logger.debug(
       "Tried to handle an Accept activity on a Join activity with a event object but the participant is already validated"
     )
 
-    nil
+    {:ok, activity, participant}
   end
 
   defp do_handle_incoming_accept_join_event(
          %Participant{role: role, event: event} = participant,
-         %Actor{} = actor_accepting
+         %Actor{} = actor_accepting,
+         _activity
        )
        when role in [:not_approved, :rejected] do
     with %Event{} = event <- Events.get_event_with_preload!(event.id),
@@ -932,7 +937,7 @@ defmodule Mobilizon.Federation.ActivityPub.Transmogrifier do
 
   # Handle incoming `Reject` activities wrapping a `Join` activity on an event
   defp do_handle_incoming_reject_join(join_object, %Actor{} = actor_accepting) do
-    with {:join_event, {:ok, %Participant{event: event, role: role} = participant}}
+    with {:join_event, {:ok, _activity, %Participant{event: event, role: role} = participant}}
          when role != :rejected <-
            {:join_event, get_participant(join_object, actor_accepting)},
          {:event, %Event{} = event} <- {:event, Events.get_event_with_preload!(event.id)},
@@ -943,7 +948,7 @@ defmodule Mobilizon.Federation.ActivityPub.Transmogrifier do
          :ok <- Participation.send_emails_to_local_user(participant) do
       {:ok, activity, participant}
     else
-      {:join_event, {:ok, %Participant{role: :rejected}}} ->
+      {:join_event, {:ok, _activity, %Participant{role: :rejected}}} ->
         Logger.warn(
           "Tried to handle an Reject activity on a Join activity with a event object but the participant is already rejected"
         )
@@ -1040,18 +1045,18 @@ defmodule Mobilizon.Federation.ActivityPub.Transmogrifier do
     end
   end
 
-  defp get_participant(join_object, %Actor{} = actor_accepting, loop \\ 1) do
+  defp get_participant(join_object, %Actor{} = actor_accepting, loop \\ 1, activity \\ nil) do
     with join_object_id when not is_nil(join_object_id) <- Utils.get_url(join_object),
          {:not_found, %Participant{} = participant} <-
            {:not_found, Events.get_participant_by_url(join_object_id)} do
-      {:ok, participant}
+      {:ok, activity, participant}
     else
       {:not_found, _err} ->
         with true <- is_map(join_object),
              true <- loop < 2,
              true <- Utils.are_same_origin?(actor_accepting.url, join_object["id"]),
-             {:ok, _activity, %Participant{url: participant_url}} <- handle_incoming(join_object) do
-          get_participant(participant_url, actor_accepting, 2)
+             {:ok, activity, %Participant{url: participant_url}} <- handle_incoming(join_object) do
+          get_participant(participant_url, actor_accepting, 2, activity)
         else
           _ ->
             {:error, "Participant URL not found"}
diff --git a/test/federation/activity_pub/transmogrifier/accept_test.exs b/test/federation/activity_pub/transmogrifier/accept_test.exs
new file mode 100644
index 000000000..41c80e2c8
--- /dev/null
+++ b/test/federation/activity_pub/transmogrifier/accept_test.exs
@@ -0,0 +1,73 @@
+defmodule Mobilizon.Federation.ActivityPub.Transmogrifier.AcceptTest do
+  use Mobilizon.DataCase
+
+  import Mox
+  alias Mobilizon.Federation.ActivityPub.Transmogrifier
+  alias Mobilizon.Service.HTTP.ActivityPub.Mock
+
+  describe "Receiving an Accept Join Event activity from a foreign instance" do
+    @base_actor_data File.read!("test/fixtures/mastodon-actor.json")
+                     |> Jason.decode!()
+    @actor_url "https://mobilizon.extinctionrebellion.fr/@anonymous"
+    @actor_data @base_actor_data
+                |> Map.put("id", @actor_url)
+                |> Map.put("preferredUsername", "anonymous")
+
+    @osmi_actor_url "https://mobilizon.extinctionrebellion.fr/@osmi"
+    @osmi_actor_data @base_actor_data
+                     |> Map.put("id", @osmi_actor_url)
+                     |> Map.put("preferredUsername", "osmi")
+
+    @xr_nantes_actor_url "https://mobilizon.extinctionrebellion.fr/@xr_nantes"
+    @xr_nantes_actor_data @base_actor_data
+                          |> Map.put("id", @xr_nantes_actor_url)
+                          |> Map.put("preferredUsername", "xr_nantes")
+
+    @event_url "https://mobilizon.extinctionrebellion.fr/events/d70f8e0d-62dc-4897-a855-ebcbe9798fc1"
+    @event_data File.read!("test/fixtures/mobilizon-post-activity.json")
+                |> Jason.decode!()
+                |> Map.get("object")
+                |> Map.put("id", @event_url)
+                |> Map.put("actor", @osmi_actor_url)
+                |> Map.put("attributedTo", @xr_nantes_actor_url)
+                |> Map.put("tag", [])
+
+    test "When the event is remote" do
+      object = %{
+        "actor" => @actor_url,
+        "id" =>
+          "https://mobilizon.extinctionrebellion.fr/join/event/b67cf172-af23-4ae8-b00e-a2e3643ccb21",
+        "object" =>
+          "https://mobilizon.extinctionrebellion.fr/events/d70f8e0d-62dc-4897-a855-ebcbe9798fc1",
+        "participationMessage" => nil,
+        "published" => "2022-03-28T20:11:11Z",
+        "type" => "Join"
+      }
+
+      activity = %{
+        "type" => "Accept",
+        "object" => object,
+        "actor" => @actor_url,
+        "id" =>
+          "https://mobilizon.extinctionrebellion.fr/join/event/b67cf172-af23-4ae8-b00e-a2e3643ccb21/activity"
+      }
+
+      Mock
+      |> expect(:call, 4, fn
+        %{method: :get, url: @actor_url}, _opts ->
+          {:ok, %Tesla.Env{status: 200, body: @actor_data}}
+
+        %{method: :get, url: @osmi_actor_url}, _opts ->
+          {:ok, %Tesla.Env{status: 200, body: @osmi_actor_data}}
+
+        %{method: :get, url: @xr_nantes_actor_url}, _opts ->
+          {:ok, %Tesla.Env{status: 200, body: @xr_nantes_actor_data}}
+
+        %{method: :get, url: @event_url}, _opts ->
+          {:ok, %Tesla.Env{status: 200, body: @event_data}}
+      end)
+
+      assert {:ok, _activity, _object} = Transmogrifier.handle_incoming(activity)
+    end
+  end
+end