diff --git a/lib/rack/passbook_rack.rb b/lib/rack/passbook_rack.rb
index 4536571..6295290 100644
--- a/lib/rack/passbook_rack.rb
+++ b/lib/rack/passbook_rack.rb
@@ -9,6 +9,7 @@ def initialize(app)
     def call(env)
       @parameters['authToken'] = env['HTTP_AUTHORIZATION'].gsub(/ApplePass /,'') if env['HTTP_AUTHORIZATION']
       @parameters.merge!(Rack::Utils.parse_nested_query(env['QUERY_STRING']))
+      @parameters['ifModifiedSince'] = env['HTTP_IF_MODIFIED_SINCE'] if env['HTTP_IF_MODIFIED_SINCE']
       method_and_params = find_method env['PATH_INFO']
       if method_and_params
         case method_and_params[:method]
@@ -25,12 +26,12 @@ def call(env)
           [response ? 200 : 204, {}, [response.to_json]]
         when 'latest_pass'
           response = Passbook::PassbookNotification.latest_pass(method_and_params[:params])
-          if response
-            [200, {'Content-Type' => 'application/vnd.apple.pkpass', 
-              'Content-Disposition' => 'attachment', 
-              'filename' => "#{method_and_params[:params]['serialNumber']}.pkpass"}, [response]]
+          if response[:status] == 200
+            [200, {'Content-Type' => 'application/vnd.apple.pkpass',
+              'Content-Disposition' => 'attachment',
+              'filename' => "#{method_and_params[:params]['serialNumber']}.pkpass","last-modified" => response[:last_modified]}, [response[:latest_pass]]]
           else
-            [204, {}, {}]
+            [response[:status], {}, {}]
           end
         when 'log'
           Passbook::PassbookNotification.passbook_log JSON.parse(env['rack.input'].read 10000)
diff --git a/spec/lib/rack/passbook_rack_spec.rb b/spec/lib/rack/passbook_rack_spec.rb
index 4a01fb4..4ba68ab 100644
--- a/spec/lib/rack/passbook_rack_spec.rb
+++ b/spec/lib/rack/passbook_rack_spec.rb
@@ -143,8 +143,8 @@
     end
 
     context 'get latest pass' do
-      context 'valid pass' do
-        let(:raw_pass) {'some url encoded text'}
+      context 'valid pass updated after if modified since' do
+        let(:raw_pass) {{:status => 200, :latest_pass => 'some url encoded text', :last_modified => '13713445412'}}
 
         before do
           Passbook::PassbookNotification.should_receive(:latest_pass).with(latest_pass_params).
@@ -154,15 +154,25 @@
 
         subject {last_response}
         its(:status) {should eq 200}
-        its(:header) {should eq({'Content-Type' => 'application/vnd.apple.pkpass', 
-          'Content-Disposition' => 'attachment', 'filename' => '27-1.pkpass', 'Content-Length' => '21'})}
-        its(:body) {should eq raw_pass}
+        its(:header) {should eq({'Content-Type' => 'application/vnd.apple.pkpass',
+          'Content-Disposition' => 'attachment', 'filename' => '27-1.pkpass', 'last-modified' => '13713445412', 'Content-Length' => '21'})}
+        its(:body) {should eq raw_pass[:latest_pass]}
+      end
+
+      context 'pass not updated after if modified since' do
+        before do
+          Passbook::PassbookNotification.should_receive(:latest_pass).with(latest_pass_params.merge!('ifModifiedSince' => '1371189712')).
+              and_return({:status => 304})
+          get latest_pass_path, {}, rack_env = {'HTTP_IF_MODIFIED_SINCE' => '1371189712'}
+        end
+        subject {last_response}
+        its(:status) {should eq 304}
       end
 
       context 'no pass' do
         before do
           Passbook::PassbookNotification.should_receive(:latest_pass).with(latest_pass_params).
-            and_return(nil)
+            and_return({:status => 204, :latest_pass => nil})
           get latest_pass_path
         end