diff --git a/netlib/http/headers.py b/netlib/http/headers.py
index 131e8ce5f..b55874ca6 100644
--- a/netlib/http/headers.py
+++ b/netlib/http/headers.py
@@ -14,6 +14,7 @@ if six.PY2:  # pragma: no cover
         return x
 
     def _always_bytes(x):
+        strutils.always_bytes(x, "utf-8", "replace")  # raises a TypeError if x != str/bytes/None.
         return x
 else:
     # While headers _should_ be ASCII, it's not uncommon for certain headers to be utf-8 encoded.
diff --git a/netlib/strutils.py b/netlib/strutils.py
index 4cb3b8056..d43c2aab0 100644
--- a/netlib/strutils.py
+++ b/netlib/strutils.py
@@ -8,7 +8,10 @@ import six
 def always_bytes(unicode_or_bytes, *encode_args):
     if isinstance(unicode_or_bytes, six.text_type):
         return unicode_or_bytes.encode(*encode_args)
-    return unicode_or_bytes
+    elif isinstance(unicode_or_bytes, bytes) or unicode_or_bytes is None:
+        return unicode_or_bytes
+    else:
+        raise TypeError("Expected str or bytes, but got {}.".format(type(unicode_or_bytes).__name__))
 
 
 def native(s, *encoding_opts):
diff --git a/pathod/language/http2.py b/pathod/language/http2.py
index c0313baa3..519ee6999 100644
--- a/pathod/language/http2.py
+++ b/pathod/language/http2.py
@@ -189,7 +189,7 @@ class Response(_HTTP2Message):
 
             resp = http.Response(
                 b'HTTP/2.0',
-                self.status_code.string(),
+                int(self.status_code.string()),
                 b'',
                 headers,
                 body,
diff --git a/pathod/protocols/http2.py b/pathod/protocols/http2.py
index a2aa91b46..7b162664a 100644
--- a/pathod/protocols/http2.py
+++ b/pathod/protocols/http2.py
@@ -6,7 +6,7 @@ import time
 import hyperframe.frame
 from hpack.hpack import Encoder, Decoder
 
-from netlib import utils, strutils
+from netlib import utils
 from netlib.http import http2
 import netlib.http.headers
 import netlib.http.response
@@ -201,7 +201,7 @@ class HTTP2StateProtocol(object):
         headers = response.headers.copy()
 
         if ':status' not in headers:
-            headers.insert(0, b':status', strutils.always_bytes(response.status_code))
+            headers.insert(0, b':status', str(response.status_code).encode())
 
         if hasattr(response, 'stream_id'):
             stream_id = response.stream_id
diff --git a/test/netlib/http/test_headers.py b/test/netlib/http/test_headers.py
index ad2bc5487..e8752c52f 100644
--- a/test/netlib/http/test_headers.py
+++ b/test/netlib/http/test_headers.py
@@ -43,6 +43,15 @@ class TestHeaders(object):
         with raises(TypeError):
             Headers([[b"Host", u"not-bytes"]])
 
+    def test_set(self):
+        headers = Headers()
+        headers[u"foo"] = u"1"
+        headers[b"bar"] = b"2"
+        headers["baz"] = b"3"
+        with raises(TypeError):
+            headers["foobar"] = 42
+        assert len(headers) == 3
+
     def test_bytes(self):
         headers = Headers(Host="example.com")
         assert bytes(headers) == b"Host: example.com\r\n"
diff --git a/test/netlib/test_strutils.py b/test/netlib/test_strutils.py
index 5be254a3e..0f58cac57 100644
--- a/test/netlib/test_strutils.py
+++ b/test/netlib/test_strutils.py
@@ -8,6 +8,8 @@ def test_always_bytes():
     assert strutils.always_bytes("foo") == b"foo"
     with tutils.raises(ValueError):
         strutils.always_bytes(u"\u2605", "ascii")
+    with tutils.raises(TypeError):
+        strutils.always_bytes(42, "ascii")
 
 
 def test_native():