diff --git a/.coveragerc b/.coveragerc
index f0624d2e..724b2872 100644
--- a/.coveragerc
+++ b/.coveragerc
@@ -1,7 +1,7 @@
 [run]
 branch = True
 source = sanic
-omit = site-packages, sanic/utils.py
+omit = site-packages, sanic/utils.py, sanic/__main__.py
 
 [html]
 directory = coverage
diff --git a/requirements-dev.txt b/requirements-dev.txt
index 674ef91d..3d94c51d 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -10,3 +10,4 @@ tox
 ujson; sys_platform != "win32" and implementation_name == "cpython"
 uvloop; sys_platform != "win32" and implementation_name == "cpython"
 gunicorn
+multidict>=4.0,<5.0
diff --git a/requirements.txt b/requirements.txt
index 05968bd8..e320e781 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,3 +3,4 @@ httptools
 ujson; sys_platform != "win32" and implementation_name == "cpython"
 uvloop; sys_platform != "win32" and implementation_name == "cpython"
 websockets>=5.0,<6.0
+multidict>=4.0,<5.0
diff --git a/sanic/cookies.py b/sanic/cookies.py
index f4cbf6a3..19daac11 100644
--- a/sanic/cookies.py
+++ b/sanic/cookies.py
@@ -47,16 +47,15 @@ class CookieJar(dict):
         super().__init__()
         self.headers = headers
         self.cookie_headers = {}
+        self.header_key = "Set-Cookie"
 
     def __setitem__(self, key, value):
         # If this cookie doesn't exist, add it to the header keys
-        cookie_header = self.cookie_headers.get(key)
-        if not cookie_header:
+        if not self.cookie_headers.get(key):
             cookie = Cookie(key, value)
             cookie['path'] = '/'
-            cookie_header = MultiHeader("Set-Cookie")
-            self.cookie_headers[key] = cookie_header
-            self.headers[cookie_header] = cookie
+            self.cookie_headers[key] = self.header_key
+            self.headers.add(self.header_key, cookie)
             return super().__setitem__(key, cookie)
         else:
             self[key].value = value
@@ -67,7 +66,11 @@ class CookieJar(dict):
             self[key]['max-age'] = 0
         else:
             cookie_header = self.cookie_headers[key]
-            del self.headers[cookie_header]
+            # remove it from header
+            cookies = self.headers.popall(cookie_header)
+            for cookie in cookies:
+                if cookie.key != key:
+                    self.headers.add(cookie_header, cookie)
             del self.cookie_headers[key]
             return super().__delitem__(key)
 
@@ -124,18 +127,3 @@ class Cookie(dict):
                 output.append('%s=%s' % (self._keys[key], value))
 
         return "; ".join(output).encode(encoding)
-
-# ------------------------------------------------------------ #
-#  Header Trickery
-# ------------------------------------------------------------ #
-
-
-class MultiHeader:
-    """String-holding object which allow us to set a header within response
-    that has a unique key, but may contain duplicate header names
-    """
-    def __init__(self, name):
-        self.name = name
-
-    def encode(self):
-        return self.name.encode()
diff --git a/sanic/response.py b/sanic/response.py
index b32e9daf..62daf91e 100644
--- a/sanic/response.py
+++ b/sanic/response.py
@@ -7,6 +7,7 @@ except BaseException:
     from json import dumps as json_dumps
 
 from aiofiles import open as open_async
+from multidict import CIMultiDict
 
 from sanic import http
 from sanic.cookies import CookieJar
@@ -53,7 +54,7 @@ class StreamingHTTPResponse(BaseHTTPResponse):
         self.content_type = content_type
         self.streaming_fn = streaming_fn
         self.status = status
-        self.headers = headers or {}
+        self.headers = CIMultiDict(headers or {})
         self._cookies = None
 
     def write(self, data):
@@ -124,7 +125,7 @@ class HTTPResponse(BaseHTTPResponse):
             self.body = body_bytes
 
         self.status = status
-        self.headers = headers or {}
+        self.headers = CIMultiDict(headers or {})
         self._cookies = None
 
     def output(
diff --git a/sanic/server.py b/sanic/server.py
index fc8291b5..11e54edc 100644
--- a/sanic/server.py
+++ b/sanic/server.py
@@ -18,6 +18,7 @@ from time import time
 
 from httptools import HttpRequestParser
 from httptools.parser.errors import HttpParserError
+from multidict import CIMultiDict
 
 try:
     import uvloop
@@ -39,25 +40,6 @@ class Signal:
     stopped = False
 
 
-class CIDict(dict):
-    """Case Insensitive dict where all keys are converted to lowercase
-    This does not maintain the inputted case when calling items() or keys()
-    in favor of speed, since headers are case insensitive
-    """
-
-    def get(self, key, default=None):
-        return super().get(key.casefold(), default)
-
-    def __getitem__(self, key):
-        return super().__getitem__(key.casefold())
-
-    def __setitem__(self, key, value):
-        return super().__setitem__(key.casefold(), value)
-
-    def __contains__(self, key):
-        return super().__contains__(key.casefold())
-
-
 class HttpProtocol(asyncio.Protocol):
     __slots__ = (
         # event loop, connection
@@ -256,7 +238,7 @@ class HttpProtocol(asyncio.Protocol):
     def on_headers_complete(self):
         self.request = self.request_class(
             url_bytes=self.url,
-            headers=CIDict(self.headers),
+            headers=CIMultiDict(self.headers),
             version=self.parser.get_http_version(),
             method=self.parser.get_method().decode(),
             transport=self.transport
diff --git a/setup.py b/setup.py
index 73cb559f..34703ab4 100644
--- a/setup.py
+++ b/setup.py
@@ -61,6 +61,7 @@ requirements = [
     ujson,
     'aiofiles>=0.3.0',
     'websockets>=5.0,<6.0',
+    'multidict>=4.0,<5.0',
 ]
 if strtobool(os.environ.get("SANIC_NO_UJSON", "no")):
     print("Installing without uJSON")
diff --git a/tests/test_cookies.py b/tests/test_cookies.py
index 84b493cb..61f50735 100644
--- a/tests/test_cookies.py
+++ b/tests/test_cookies.py
@@ -25,6 +25,7 @@ def test_cookies():
     assert response.text == 'Cookies are: working!'
     assert response_cookies['right_back'].value == 'at you'
 
+
 @pytest.mark.parametrize("httponly,expected", [
         (False, False),
         (True, True),
diff --git a/tests/test_response.py b/tests/test_response.py
index 12049460..36259970 100644
--- a/tests/test_response.py
+++ b/tests/test_response.py
@@ -64,6 +64,25 @@ def test_method_not_allowed():
     assert response.headers['Content-Length'] == '0'
 
 
+def test_response_header():
+    app = Sanic('test_response_header')
+    @app.get('/')
+    async def test(request):
+        return json({
+            "ok": True
+        }, headers={
+            'CONTENT-TYPE': 'application/json'
+        })
+
+    request, response = app.test_client.get('/')
+    assert dict(response.headers) == {
+        'Connection': 'keep-alive',
+        'Keep-Alive': '2',
+        'Content-Length': '11',
+        'Content-Type': 'application/json',
+    }
+
+
 @pytest.fixture
 def json_app():
     app = Sanic('json')