diff --git a/tornado/httputil.py b/tornado/httputil.py
index b9cd1065..f68c7414 100644
--- a/tornado/httputil.py
+++ b/tornado/httputil.py
@@ -236,6 +236,8 @@ def parse_body_arguments(content_type, body, arguments, files):
         uri_arguments = parse_qs_bytes(native_str(body))
         for name, values in uri_arguments.items():
             values = [v for v in values if v]
+        uri_arguments = parse_qs_bytes(native_str(body), keep_blank_values=True)
+        for name, values in uri_arguments.items():
             if values:
                 arguments.setdefault(name, []).extend(values)
     elif content_type.startswith("multipart/form-data"):
diff --git a/tornado/test/httpserver_test.py b/tornado/test/httpserver_test.py
index 123ae2e7..54b38b46 100644
--- a/tornado/test/httpserver_test.py
+++ b/tornado/test/httpserver_test.py
@@ -258,6 +258,8 @@ class EchoHandler(RequestHandler):
     def get(self):
         self.write(recursive_unicode(self.request.arguments))
 
+    def post(self):
+        self.write(recursive_unicode(self.request.arguments))
 
 class TypeCheckHandler(RequestHandler):
     def prepare(self):
@@ -316,6 +318,11 @@ class HTTPServerTest(AsyncHTTPTestCase):
         data = json_decode(response.body)
         self.assertEqual(data, {u("foo"): [u(""), u("")]})
 
+    def test_empty_post_parameters(self):
+        response = self.fetch("/echo", method="POST", body="foo=&bar=")
+        data = json_decode(response.body)
+        self.assertEqual(data, {u("foo"): [u("")], u("bar"): [u("")]})
+
     def test_types(self):
         headers = {"Cookie": "foo=bar"}
         response = self.fetch("/typecheck?foo=bar", headers=headers)