diff --git a/lib/twirp/plug.ex b/lib/twirp/plug.ex
index 7ee4cb9..3f3e31c 100644
--- a/lib/twirp/plug.ex
+++ b/lib/twirp/plug.ex
@@ -105,7 +105,7 @@ defmodule Twirp.Plug do
         Telemetry.stop(:call, start, metadata)
 
         conn
-        |> put_resp_content_type(env.content_type)
+        |> put_resp_content_type(env.content_type, nil)
         |> send_resp(200, resp)
         |> halt()
       else
@@ -279,11 +279,10 @@ defmodule Twirp.Plug do
   end
 
   defp send_error(conn, error) do
-    content_type = Encoder.type(:json)
-    body = Encoder.encode(error, nil, content_type)
+    body = Jason.encode!(error)
 
     conn
-    |> put_resp_content_type(content_type)
+    |> put_resp_content_type("application/json", nil)
     |> send_resp(Error.code_to_status(error.code), body)
     |> halt()
   end
diff --git a/test/twirp/plug_test.exs b/test/twirp/plug_test.exs
index 737c6b5..6559174 100644
--- a/test/twirp/plug_test.exs
+++ b/test/twirp/plug_test.exs
@@ -73,10 +73,9 @@ defmodule Twirp.PlugTest do
   end
 
   def content_type(conn) do
-    conn.resp_headers
-    |> Enum.find_value(fn {h, v} -> if h == "content-type", do: v, else: false end)
-    |> String.split(";") # drop the charset if there is one
-    |> Enum.at(0)
+   Enum.find_value(conn.resp_headers, fn {h, v} ->
+      if h == "content-type", do: v, else: false
+    end)
   end
 
   def call(req, opts \\ @opts) do
@@ -112,6 +111,16 @@ defmodule Twirp.PlugTest do
     assert conn == req
   end
 
+  test "does not include the __exception__ field" do
+    req = conn(:get, "/twirp/plug.test.Haberdasher/MakeHat")
+    conn = call(req)
+
+    assert conn.status == 404
+    assert content_type(conn) == "application/json"
+    body = Jason.decode!(conn.resp_body)
+    refute Map.has_key?(body, "__exception__")
+  end
+
   test "not a POST" do
     req = conn(:get, "/twirp/plug.test.Haberdasher/MakeHat")
     conn = call(req)
@@ -299,7 +308,7 @@ defmodule Twirp.PlugTest do
     resp = Jason.decode!(conn.resp_body)
     assert resp["code"] == "internal"
     assert resp["msg"] == "Blow this ish up"
-    assert resp["meta"] == %{}
+    refute Map.has_key?(resp, "meta")
   end
 
   describe "before" do