diff --git a/lib/pleroma/web/activity_pub/mrf/force_mentions_in_content.ex b/lib/pleroma/web/activity_pub/mrf/force_mentions_in_content.ex
index b9b175cc3..5532093cb 100644
--- a/lib/pleroma/web/activity_pub/mrf/force_mentions_in_content.ex
+++ b/lib/pleroma/web/activity_pub/mrf/force_mentions_in_content.ex
@@ -95,11 +95,13 @@ def filter(
       |> Enum.reject(&is_nil/1)
       |> sort_replied_user(replied_to_user)
 
-    explicitly_mentioned_uris = extract_mention_uris_from_content(content)
+    explicitly_mentioned_uris =
+      extract_mention_uris_from_content(content)
+      |> MapSet.new()
 
     added_mentions =
-      Enum.reduce(mention_users, "", fn %User{ap_id: api_id, uri: uri} = user, acc ->
-        unless Enum.any?([api_id, uri], fn u -> u in explicitly_mentioned_uris end) do
+      Enum.reduce(mention_users, "", fn %User{ap_id: ap_id, uri: uri} = user, acc ->
+        if MapSet.disjoint?(MapSet.new([ap_id, uri]), explicitly_mentioned_uris) do
           acc <> Formatter.mention_from_user(user, %{mentions_format: :compact}) <> " "
         else
           acc
diff --git a/test/pleroma/web/activity_pub/mrf/force_mentions_in_content_test.exs b/test/pleroma/web/activity_pub/mrf/force_mentions_in_content_test.exs
index 5ebd972a6..811ef105c 100644
--- a/test/pleroma/web/activity_pub/mrf/force_mentions_in_content_test.exs
+++ b/test/pleroma/web/activity_pub/mrf/force_mentions_in_content_test.exs
@@ -282,7 +282,7 @@ test "don't add duplicate mentions for mastodon or misskey posts" do
     {:ok, post} = CommonAPI.post(rogerick, %{status: "eugh"})
 
     inline_mentions = [
-      "<span class=\"h-card\"><a class=\"u-url mention\" data-user=\"#{rogerick.id}\" href=\"#{rogerick.uri}\" rel=\"ugc\">@<span>rogerick</span></a></span>",
+      "<span class=\"h-card\"><a class=\"u-url mention\" data-user=\"#{rogerick.id}\" href=\"#{rogerick.ap_id}\" rel=\"ugc\">@<span>rogerick</span></a></span>",
       "<span class=\"h-card\"><a class=\"u-url mention\" data-user=\"#{greg.id}\" href=\"#{greg.uri}\" rel=\"ugc\">@<span>greg</span></a></span>"
     ]