diff --git a/lib/web_console.rb b/lib/web_console.rb
index 0ba155a4..04c8cae9 100644
--- a/lib/web_console.rb
+++ b/lib/web_console.rb
@@ -10,7 +10,7 @@ module WebConsole
   autoload :Evaluator
   autoload :ExceptionMapper
   autoload :Session
-  autoload :Response
+  autoload :Injector
   autoload :Request
   autoload :WhinyRequest
   autoload :Whitelist
diff --git a/lib/web_console/injector.rb b/lib/web_console/injector.rb
new file mode 100644
index 00000000..03773995
--- /dev/null
+++ b/lib/web_console/injector.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+module WebConsole
+  # Injects content into a Rack body.
+  class Injector
+    def initialize(body)
+      @body = "".dup
+
+      body.each { |part| @body << part }
+      body.close if body.respond_to?(:close)
+    end
+
+    def inject(content)
+      if position = @body.rindex("</body>")
+        [ @body.insert(position, content) ]
+      else
+        [ @body << content ]
+      end
+    end
+  end
+end
diff --git a/lib/web_console/middleware.rb b/lib/web_console/middleware.rb
index e8f26746..ece9cdd0 100644
--- a/lib/web_console/middleware.rb
+++ b/lib/web_console/middleware.rb
@@ -30,16 +30,14 @@ def call(env)
         status, headers, body = call_app(env)
 
         if (session = Session.from(Thread.current)) && acceptable_content_type?(headers)
-          response = Response.new(body, status, headers)
-          template = Template.new(env, session)
+          headers["X-Web-Console-Session-Id"] = session.id
+          headers["X-Web-Console-Mount-Point"] = mount_point
 
-          response.headers["X-Web-Console-Session-Id"] = session.id
-          response.headers["X-Web-Console-Mount-Point"] = mount_point
-          response.write(template.render("index"))
-          response.finish
-        else
-          [ status, headers, body ]
+          template = Template.new(env, session)
+          body = Injector.new(body).inject(template.render("index"))
         end
+
+        [ status, headers, body ]
       end
     rescue => e
       WebConsole.logger.error("\n#{e.class}: #{e}\n\tfrom #{e.backtrace.join("\n\tfrom ")}")
@@ -64,7 +62,7 @@ def json_response(opts = {})
         headers = { "Content-Type" => "application/json; charset = utf-8" }
         body    = yield.to_json
 
-        Rack::Response.new(body, status, headers).finish
+        [ status, headers, [ body ] ]
       end
 
       def json_response_with_session(id, request, opts = {})
diff --git a/lib/web_console/response.rb b/lib/web_console/response.rb
deleted file mode 100644
index 350b6d54..00000000
--- a/lib/web_console/response.rb
+++ /dev/null
@@ -1,27 +0,0 @@
-# frozen_string_literal: true
-
-module WebConsole
-  # A response object that writes content before the closing </body> tag, if
-  # possible.
-  #
-  # The object quacks like Rack::Response.
-  class Response < Struct.new(:body, :status, :headers)
-    def write(content)
-      raw_body = Array(body).first.to_s
-
-      # We're done with the original body object, so make sure to close it to comply with the Rack SPEC
-      body.close if body.respond_to?(:close)
-
-      self.body =
-        if position = raw_body.rindex("</body>")
-          raw_body.dup.insert(position, content)
-        else
-          raw_body.dup << content
-        end
-    end
-
-    def finish
-      Rack::Response.new(body, status, headers).finish
-    end
-  end
-end
diff --git a/test/web_console/injector_test.rb b/test/web_console/injector_test.rb
new file mode 100644
index 00000000..434fae9c
--- /dev/null
+++ b/test/web_console/injector_test.rb
@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+require "test_helper"
+
+module WebConsole
+  class InjectorTest < ActiveSupport::TestCase
+    test "closes body if closable" do
+      closed = false
+
+      body = [ "foo" ]
+      body.define_singleton_method(:close) { closed = true }
+
+      assert_equal [ "foobar" ], Injector.new(body).inject("bar")
+      assert closed
+    end
+
+    test "support fancy bodies like Rack::BodyProxy" do
+      closed = false
+      body = Rack::BodyProxy.new([ "foo" ]) { closed = true }
+
+      assert_equal [ "foobar" ], Injector.new(body).inject("bar")
+      assert closed
+    end
+
+    test "support fancy bodies like ActionDispatch::Response::RackBody" do
+      body = ActionDispatch::Response.create(200, {}, [ "foo" ]).to_a.last
+
+      assert_equal [ "foobar" ], Injector.new(body).inject("bar")
+    end
+  end
+end