diff --git a/activeresource/lib/active_resource/http_mock.rb b/activeresource/lib/active_resource/http_mock.rb
index ddd3fb1f5dc86c5affc79ea3ed42666d693c483c..2250ed9c044eb81dfc7d4cbacd70172497b3cc22 100644
--- a/activeresource/lib/active_resource/http_mock.rb
+++ b/activeresource/lib/active_resource/http_mock.rb
@@ -100,11 +100,11 @@ def responses
 
       # Accepts a block which declares a set of requests and responses for the HttpMock to respond to in
       # the following format:
-      # 
+      #
       #   mock.http_method(path, request_headers = {}, body = nil, status = 200, response_headers = {})
-      # 
+      #
       # === Example
-      # 
+      #
       #   @matz  = { :id => 1, :name => "Matz" }.to_xml(:root => "person")
       #   ActiveResource::HttpMock.respond_to do |mock|
       #     mock.post   "/people.xml",   {}, @matz, 201, "Location" => "/people/1.xml"
@@ -112,58 +112,58 @@ def responses
       #     mock.put    "/people/1.xml", {}, nil, 204
       #     mock.delete "/people/1.xml", {}, nil, 200
       #   end
-      # 
+      #
       # Alternatively, accepts a hash of <tt>{Request => Response}</tt> pairs allowing you to generate
       # these the following format:
-      # 
+      #
       #   ActiveResource::Request.new(method, path, body, request_headers)
       #   ActiveResource::Response.new(body, status, response_headers)
-      # 
+      #
       # === Example
-      # 
+      #
       # Request.new(:#{method}, path, nil, request_headers)
-      # 
+      #
       #   @matz  = { :id => 1, :name => "Matz" }.to_xml(:root => "person")
       #
       #   create_matz      = ActiveResource::Request.new(:post, '/people.xml', @matz, {})
       #   created_response = ActiveResource::Response.new("", 201, {"Location" => "/people/1.xml"})
       #   get_matz         = ActiveResource::Request.new(:get, '/people/1.xml', nil)
       #   ok_response      = ActiveResource::Response.new("", 200, {})
-      # 
+      #
       #   pairs = {create_matz => created_response, get_matz => ok_response}
-      # 
+      #
       #   ActiveResource::HttpMock.respond_to(pairs)
       #
       # Note, by default, every time you call +respond_to+, any previous request and response pairs stored
       # in HttpMock will be deleted giving you a clean slate to work on.
-      # 
+      #
       # If you want to override this behaviour, pass in +false+ as the last argument to +respond_to+
-      # 
+      #
       # === Example
-      # 
+      #
       #   ActiveResource::HttpMock.respond_to do |mock|
       #     mock.send(:get, "/people/1", {}, "XML1")
       #   end
       #   ActiveResource::HttpMock.responses.length #=> 1
-      #   
+      #
       #   ActiveResource::HttpMock.respond_to(false) do |mock|
       #     mock.send(:get, "/people/2", {}, "XML2")
       #   end
       #   ActiveResource::HttpMock.responses.length #=> 2
-      # 
+      #
       # This also works with passing in generated pairs of requests and responses, again, just pass in false
       # as the last argument:
-      # 
+      #
       # === Example
-      # 
+      #
       #   ActiveResource::HttpMock.respond_to do |mock|
       #     mock.send(:get, "/people/1", {}, "XML1")
       #   end
       #   ActiveResource::HttpMock.responses.length #=> 1
-      # 
+      #
       #   get_matz         = ActiveResource::Request.new(:get, '/people/1.xml', nil)
       #   ok_response      = ActiveResource::Response.new("", 200, {})
-      # 
+      #
       #   pairs = {get_matz => ok_response}
       #
       #   ActiveResource::HttpMock.respond_to(pairs, false)
@@ -171,6 +171,8 @@ def responses
       def respond_to(*args) #:yields: mock
         pairs = args.first || {}
         reset! if args.last.class != FalseClass
+
+        delete_responses_to_replace pairs.to_a
         responses.concat pairs.to_a
         if block_given?
           yield Responder.new(responses)
@@ -179,6 +181,13 @@ def respond_to(*args) #:yields: mock
         end
       end
 
+      def delete_responses_to_replace(new_responses)
+        new_responses.each{|nr|
+          request_to_remove = nr[0]
+          @@responses = responses.delete_if{|r| r[0] == request_to_remove}
+        }
+      end
+
       # Deletes all logged requests and responses.
       def reset!
         requests.clear
diff --git a/activeresource/test/cases/http_mock_test.rb b/activeresource/test/cases/http_mock_test.rb
index d90d1e01b88b70ba5f398156a338e08484e38acc..f15ad04b9a5f7b5d8dc1d94dbfa00c87f48f2952 100644
--- a/activeresource/test/cases/http_mock_test.rb
+++ b/activeresource/test/cases/http_mock_test.rb
@@ -69,19 +69,19 @@ class HttpMockTest < ActiveSupport::TestCase
         request(method, "/people/1", FORMAT_HEADER[method] => "application/json")
       end
     end
-    
+
   end
 
   test "allows you to send in pairs directly to the respond_to method" do
     matz  = { :id => 1, :name => "Matz" }.to_xml(:root => "person")
-    
+
     create_matz = ActiveResource::Request.new(:post, '/people.xml', matz, {})
     created_response = ActiveResource::Response.new("", 201, {"Location" => "/people/1.xml"})
     get_matz = ActiveResource::Request.new(:get, '/people/1.xml', nil)
     ok_response = ActiveResource::Response.new(matz, 200, {})
-    
+
     pairs = {create_matz => created_response, get_matz => ok_response}
-    
+
     ActiveResource::HttpMock.respond_to(pairs)
     assert_equal 2, ActiveResource::HttpMock.responses.length
     assert_equal "", ActiveResource::HttpMock.responses.assoc(create_matz)[1].body
@@ -140,6 +140,21 @@ class HttpMockTest < ActiveSupport::TestCase
     assert_equal 2, ActiveResource::HttpMock.responses.length
   end
 
+  test "allows you to add replace the existing reponese with the same path" do
+    ActiveResource::HttpMock.respond_to do |mock|
+      mock.send(:get, "/people/1", {}, "XML1")
+    end
+    assert_equal 1, ActiveResource::HttpMock.responses.length
+
+    matz  = { :id => 1, :name => "Matz" }.to_xml(:root => "person")
+    get_matz = ActiveResource::Request.new(:get, '/people/1', nil)
+    ok_response = ActiveResource::Response.new(matz, 200, {})
+
+    ActiveResource::HttpMock.respond_to({get_matz => ok_response}, false)
+
+    assert_equal 1, ActiveResource::HttpMock.responses.length
+  end
+
   def request(method, path, headers = {}, body = nil)
     if [:put, :post].include? method
       @http.send(method, path, body, headers)