diff --git a/lib/pleroma/signature.ex b/lib/pleroma/signature.ex
index 6b0b2c969..d01728361 100644
--- a/lib/pleroma/signature.ex
+++ b/lib/pleroma/signature.ex
@@ -8,6 +8,7 @@ defmodule Pleroma.Signature do
   alias Pleroma.Keys
   alias Pleroma.User
   alias Pleroma.Web.ActivityPub.ActivityPub
+  alias Pleroma.Web.ActivityPub.ObjectValidators.Types
 
   def key_id_to_actor_id(key_id) do
     uri =
@@ -21,12 +22,23 @@ defmodule Pleroma.Signature do
         uri
       end
 
-    URI.to_string(uri)
+    maybe_ap_id = URI.to_string(uri)
+
+    case Types.ObjectID.cast(maybe_ap_id) do
+      {:ok, ap_id} ->
+        {:ok, ap_id}
+
+      _ ->
+        case Pleroma.Web.WebFinger.finger(maybe_ap_id) do
+          %{"ap_id" => ap_id} -> {:ok, ap_id}
+          _ -> {:error, maybe_ap_id}
+        end
+    end
   end
 
   def fetch_public_key(conn) do
     with %{"keyId" => kid} <- HTTPSignatures.signature_for_conn(conn),
-         actor_id <- key_id_to_actor_id(kid),
+         {:ok, actor_id} <- key_id_to_actor_id(kid),
          {:ok, public_key} <- User.get_public_key_for_ap_id(actor_id) do
       {:ok, public_key}
     else
@@ -37,7 +49,7 @@ defmodule Pleroma.Signature do
 
   def refetch_public_key(conn) do
     with %{"keyId" => kid} <- HTTPSignatures.signature_for_conn(conn),
-         actor_id <- key_id_to_actor_id(kid),
+         {:ok, actor_id} <- key_id_to_actor_id(kid),
          {:ok, _user} <- ActivityPub.make_user_from_ap_id(actor_id),
          {:ok, public_key} <- User.get_public_key_for_ap_id(actor_id) do
       {:ok, public_key}
diff --git a/test/signature_test.exs b/test/signature_test.exs
index d5a2a62c4..a7a75aa4d 100644
--- a/test/signature_test.exs
+++ b/test/signature_test.exs
@@ -44,7 +44,8 @@ defmodule Pleroma.SignatureTest do
 
     test "it returns error when not found user" do
       assert capture_log(fn ->
-               assert Signature.fetch_public_key(make_fake_conn("test-ap_id")) == {:error, :error}
+               assert Signature.fetch_public_key(make_fake_conn("https://test-ap-id")) ==
+                        {:error, :error}
              end) =~ "[error] Could not decode user"
     end
 
@@ -64,7 +65,7 @@ defmodule Pleroma.SignatureTest do
 
     test "it returns error when not found user" do
       assert capture_log(fn ->
-               {:error, _} = Signature.refetch_public_key(make_fake_conn("test-ap_id"))
+               {:error, _} = Signature.refetch_public_key(make_fake_conn("https://test-ap_id"))
              end) =~ "[error] Could not decode user"
     end
   end
@@ -100,12 +101,21 @@ defmodule Pleroma.SignatureTest do
   describe "key_id_to_actor_id/1" do
     test "it properly deduces the actor id for misskey" do
       assert Signature.key_id_to_actor_id("https://example.com/users/1234/publickey") ==
-               "https://example.com/users/1234"
+               {:ok, "https://example.com/users/1234"}
     end
 
     test "it properly deduces the actor id for mastodon and pleroma" do
       assert Signature.key_id_to_actor_id("https://example.com/users/1234#main-key") ==
-               "https://example.com/users/1234"
+               {:ok, "https://example.com/users/1234"}
+    end
+
+    test "it calls webfinger for 'acct:' accounts" do
+      with_mock(Pleroma.Web.WebFinger,
+        finger: fn _ -> %{"ap_id" => "https://gensokyo.2hu/users/raymoo"} end
+      ) do
+        assert Signature.key_id_to_actor_id("acct:raymoo@gensokyo.2hu") ==
+                 {:ok, "https://gensokyo.2hu/users/raymoo"}
+      end
     end
   end