diff --git a/lib/phoenix/socket.ex b/lib/phoenix/socket.ex
index 8a8a3d69ac..448d16117f 100644
--- a/lib/phoenix/socket.ex
+++ b/lib/phoenix/socket.ex
@@ -676,7 +676,8 @@ defmodule Phoenix.Socket do
             state = put_channel(state, pid, topic, join_ref)
 
             num_channels = map_size(state.channels)
-            :telemetry.execute([:phoenix, :socket, :joined_channels], %{total: num_channels})
+            metadata = %{assigns: socket.assigns}
+            :telemetry.execute([:phoenix, :socket, :joined_channels], %{total: num_channels}, metadata)
             {:reply, :ok, encode_reply(socket, reply), {state, socket}}
 
           {:error, reply} ->