diff --git a/lib/sinatra/base.rb b/lib/sinatra/base.rb
index 72679880..9e034bf5 100644
--- a/lib/sinatra/base.rb
+++ b/lib/sinatra/base.rb
@@ -435,6 +435,9 @@ module Sinatra
       # No matching route found or all routes passed -- forward downstream
       # when running as middleware; 404 when running as normal app.
       if @app
+        # Call bypassed method before forward to catch behavior that should
+        # happen even if no routes are hit.
+        bypassed if respond_to?(:bypassed)
         forward
       else
         raise NotFound
diff --git a/test/base_test.rb b/test/base_test.rb
index 856f0499..aab3869a 100644
--- a/test/base_test.rb
+++ b/test/base_test.rb
@@ -42,7 +42,7 @@ end
 describe "Sinatra::Base as Rack middleware" do
 
   app = lambda { |env|
-    [210, {'X-Downstream' => 'true'}, ['Hello from downstream']] }
+    [210, {'X-Downstream' => 'true', 'X-Bypass-Test' => '1' || ''}, ['Hello from downstream']] }
 
   class TestMiddleware < Sinatra::Base
   end
@@ -58,6 +58,10 @@ describe "Sinatra::Base as Rack middleware" do
   end
 
   class TestMiddleware < Sinatra::Base
+    def bypassed
+      env['X-Bypass-Test'] = '1'
+    end
+
     get '/' do
       'Hello from middleware'
     end
@@ -78,6 +82,11 @@ describe "Sinatra::Base as Rack middleware" do
     assert_equal 'Hello from downstream', response.body
   end
 
+  it 'calls #bypassed before forwarding downstream' do
+    response = request.get('/missing')
+    assert_equal '1', response['X-Bypass-Test']
+  end
+
   class TestMiddleware < Sinatra::Base
     get '/low-level-forward' do
       app.call(env)