diff --git a/CHANGES.rst b/CHANGES.rst
index 3bef822885..f85c5d9572 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -61,6 +61,9 @@ CHANGES
 - Remove aiohttp.websocket module (BACKWARD IMCOMPATIBLE)
   Please use high-level client and server approaches
 
+- Link header for 451 status code is mandatory
+
+
 0.22.5 (08-02-2016)
 -------------------
 
diff --git a/aiohttp/web_exceptions.py b/aiohttp/web_exceptions.py
index 4b226dbdf0..b886697a5d 100644
--- a/aiohttp/web_exceptions.py
+++ b/aiohttp/web_exceptions.py
@@ -289,13 +289,12 @@ class HTTPRequestHeaderFieldsTooLarge(HTTPClientError):
 class HTTPUnavailableForLegalReasons(HTTPClientError):
     status_code = 451
 
-    def __init__(self, link=None, *, headers=None, reason=None,
+    def __init__(self, link, *, headers=None, reason=None,
                  body=None, text=None, content_type=None):
         super().__init__(headers=headers, reason=reason,
                          body=body, text=text, content_type=content_type)
-        if link:
-            self.headers['Link'] = '<%s>; rel="blocked-by"' % link
-            self.link = link
+        self.headers['Link'] = '<%s>; rel="blocked-by"' % link
+        self.link = link
 
 
 ############################################################