diff --git a/CHANGELOG.md b/CHANGELOG.md
index 57cc42cf4..3ed7442d1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -26,6 +26,7 @@ All notable changes to this project will be documented in this file. For info on
 - Decrease default allowed parameter recursion level from 100 to 32. ([#1640](https://github.com/rack/rack/issues/1640), [@jeremyevans](https://github.com/jeremyevans))
 - Attempting to parse a multipart response with an empty body now raises Rack::Multipart::EmptyContentError. ([#1603](https://github.com/rack/rack/issues/1603), [@jeremyevans](https://github.com/jeremyevans))
 - `Rack::Utils.secure_compare` uses OpenSSL's faster implementation if available. ([#1711](https://github.com/rack/rack/pull/1711), [@bdewater](https://github.com/bdewater))
+- `Rack::Request#POST` now caches an empty hash if input content type is not parseable. ([#749](https://github.com/rack/rack/pull/749), [@jeremyevans](https://github.com/jeremyevans))
 - BREAKING CHANGE: Updated `trusted_proxy?` to match full 127.0.0.0/8 network. ([#1781](https://github.com/rack/rack/pull/1781), [@snbloch](https://github.com/snbloch))
 
 ### Fixed
diff --git a/lib/rack/request.rb b/lib/rack/request.rb
index 722a06b8d..2df93ebd9 100644
--- a/lib/rack/request.rb
+++ b/lib/rack/request.rb
@@ -471,7 +471,8 @@ def POST
           set_header RACK_REQUEST_FORM_INPUT, get_header(RACK_INPUT)
           get_header RACK_REQUEST_FORM_HASH
         else
-          {}
+          set_header RACK_REQUEST_FORM_INPUT, get_header(RACK_INPUT)
+          set_header(RACK_REQUEST_FORM_HASH, {})
         end
       end
 
diff --git a/test/spec_request.rb b/test/spec_request.rb
index c2c71dc4b..7371823a3 100644
--- a/test/spec_request.rb
+++ b/test/spec_request.rb
@@ -434,7 +434,9 @@ def initialize(*)
     req.media_type.must_equal 'text/plain'
     req.media_type_params['charset'].must_equal 'utf-8'
     req.content_charset.must_equal 'utf-8'
-    req.POST.must_be :empty?
+    post = req.POST
+    post.must_be_empty
+    req.POST.must_be_same_as post
     req.params.must_equal "foo" => "quux"
     req.body.read.must_equal "foo=bar&quux=bla"
   end