diff --git a/actionpack/CHANGELOG b/actionpack/CHANGELOG
index b95b003c2d0d4ee6d1389aaca1620b0642587a78..225d0c031925713b5e5a39d9eb2d171b72f31d36 100644
--- a/actionpack/CHANGELOG
+++ b/actionpack/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Enhance documentation for setting headers in integration tests. Skip auto HTTP prepending when its already there. Closes #4079. [Rick Olson]
+
 * Documentation for AbstractRequest. Closes #4895. [kevin.clark@gmail.com] 
 
 * Refactor various InstanceTag instance method to class methods. Closes #4800. [skaes@web.de]
diff --git a/actionpack/lib/action_controller/integration.rb b/actionpack/lib/action_controller/integration.rb
index 33ec1a01071dc5848c7987f4e4c3dd55aa17a39f..c96dd9c5130510afa051bc20ccafe783288f61b0 100644
--- a/actionpack/lib/action_controller/integration.rb
+++ b/actionpack/lib/action_controller/integration.rb
@@ -140,14 +140,18 @@ def redirect?
 
       # Performs a GET request with the given parameters. The parameters may
       # be +nil+, a Hash, or a string that is appropriately encoded
-      # (application/x-www-form-urlencoded or multipart/form-data).
+      # (application/x-www-form-urlencoded or multipart/form-data).  The headers
+      # should be a hash.  The keys will automatically be upcased, with the 
+      # prefix 'HTTP_' added if needed.
       def get(path, parameters=nil, headers=nil)
         process :get, path, parameters, headers
       end
 
       # Performs a POST request with the given parameters. The parameters may
       # be +nil+, a Hash, or a string that is appropriately encoded
-      # (application/x-www-form-urlencoded or multipart/form-data).
+      # (application/x-www-form-urlencoded or multipart/form-data).  The headers
+      # should be a hash.  The keys will automatically be upcased, with the 
+      # prefix 'HTTP_' added if needed.
       def post(path, parameters=nil, headers=nil)
         process :post, path, parameters, headers
       end
@@ -155,7 +159,9 @@ def post(path, parameters=nil, headers=nil)
       # Performs an XMLHttpRequest request with the given parameters, mimicing
       # the request environment created by the Prototype library. The parameters
       # may be +nil+, a Hash, or a string that is appropriately encoded
-      # (application/x-www-form-urlencoded or multipart/form-data).
+      # (application/x-www-form-urlencoded or multipart/form-data).  The headers
+      # should be a hash.  The keys will automatically be upcased, with the 
+      # prefix 'HTTP_' added if needed.
       def xml_http_request(path, parameters=nil, headers=nil)
         headers = (headers || {}).merge("X-Requested-With" => "XMLHttpRequest")
         post(path, parameters, headers)
@@ -218,7 +224,7 @@ def process(method, path, parameters=nil, headers=nil)
 
           (headers || {}).each do |key, value|
             key = key.to_s.upcase.gsub(/-/, "_")
-            key = "HTTP_#{key}" unless env.has_key?(key)
+            key = "HTTP_#{key}" unless env.has_key?(key) || env =~ /^X|HTTP/
             env[key] = value
           end