diff --git a/aiohttp/protocol.py b/aiohttp/protocol.py
index b5fac701764..daaefafc87a 100644
--- a/aiohttp/protocol.py
+++ b/aiohttp/protocol.py
@@ -11,6 +11,7 @@
 import http.server
 import itertools
 import re
+import string
 import sys
 import zlib
 from wsgiref.handlers import format_date_time
@@ -20,6 +21,7 @@
 from aiohttp import multidict
 from aiohttp.log import internal_log
 
+ASCIISET = set(string.printable)
 METHRE = re.compile('[A-Z0-9$-_.]+')
 VERSRE = re.compile('HTTP/(\d+).(\d+)')
 HDRRE = re.compile('[\x00-\x1F\x7F()<>@,;:\[\]={} \t\\\\\"]')
@@ -572,8 +574,12 @@ def add_header(self, name, value):
         """Analyze headers. Calculate content length,
         removes hop headers, etc."""
         assert not self.headers_sent, 'headers have been sent already'
-        assert isinstance(name, str), '{!r} is not a string'.format(name)
-        assert isinstance(value, str), '{!r} is not a string'.format(value)
+        assert isinstance(name, str), \
+            'Header name should be a string, got {!r}'.format(name)
+        assert set(name).issubset(ASCIISET), \
+            'Header name should contain ASCII chars, got {!r}'.format(name)
+        assert isinstance(value, str), \
+            'Header {!r} should have string value, got {!r}'.format(name, value)
 
         name = name.strip().upper()
         value = value.strip()
diff --git a/tests/test_http_protocol.py b/tests/test_http_protocol.py
index 27f172f9657..7d7775c3a3d 100644
--- a/tests/test_http_protocol.py
+++ b/tests/test_http_protocol.py
@@ -76,12 +76,22 @@ def test_add_header_with_spaces(self):
         self.assertEqual(
             [('CONTENT-TYPE', 'plain/html')], list(msg.headers.items()))
 
+    def test_add_header_non_ascii(self):
+        msg = protocol.Response(self.transport, 200)
+        self.assertEqual([], list(msg.headers))
+
+        with self.assertRaises(AssertionError):
+            msg.add_header('тип-контента', 'текст/плейн')
+
     def test_add_header_invalid_value_type(self):
         msg = protocol.Response(self.transport, 200)
         self.assertEqual([], list(msg.headers))
 
         with self.assertRaises(AssertionError):
-            msg.add_header('content-type', b'value')
+            msg.add_header('content-type', {'test': 'plain'})
+
+        with self.assertRaises(AssertionError):
+            msg.add_header(list('content-type'), 'text/plain')
 
     def test_add_headers(self):
         msg = protocol.Response(self.transport, 200)