diff --git a/Lib/http/client.py b/Lib/http/client.py
--- a/Lib/http/client.py
+++ b/Lib/http/client.py
@@ -597,17 +597,21 @@ class HTTPResponse(io.RawIOBase):
         return b"".join(s)
 
     def fileno(self):
         return self.fp.fileno()
 
     def getheader(self, name, default=None):
         if self.headers is None:
             raise ResponseNotReady()
-        return ', '.join(self.headers.get_all(name, default))
+        headers = self.headers.get_all(name) or default
+        if not headers or isinstance(headers, str):
+            return headers
+        else:
+            return ', '.join(headers)
 
     def getheaders(self):
         """Return list of (header, value) tuples."""
         if self.headers is None:
             raise ResponseNotReady()
         return list(self.headers.items())
 
     # We override IOBase.__iter__ so that it doesn't check for closed-ness
diff --git a/Lib/test/test_httplib.py b/Lib/test/test_httplib.py
--- a/Lib/test/test_httplib.py
+++ b/Lib/test/test_httplib.py
@@ -437,14 +437,47 @@ class RequestBodyTest(TestCase):
         f = open(support.TESTFN, "rb")
         self.conn.request("PUT", "/url", f)
         message, f = self.get_headers_and_fp()
         self.assertEqual("text/plain", message.get_content_type())
         self.assertEqual(None, message.get_charset())
         self.assertEqual("5", message.get("content-length"))
         self.assertEqual(b'body\xc1', f.read())
 
+
+class HTTPResponseTest(TestCase):
+
+    def setUp(self):
+        body = "HTTP/1.1 200 Ok\r\nMy-Header: actual-value\r\n\r\nText"
+        sock = FakeSocket(body)
+        self.resp = client.HTTPResponse(sock)
+        self.resp.begin()
+
+    def test_getting_header(self):
+        header = self.resp.getheader('My-Header')
+        self.assertEqual(header, 'actual-value')
+
+        header = self.resp.getheader('My-Header', 'some default')
+        self.assertEqual(header, 'actual-value')
+
+    def test_getting_nonexistent_header_with_string_default(self):
+        header = self.resp.getheader('No-Such-Header', 'default-value')
+        self.assertEqual(header, 'default-value')
+
+    def test_getting_nonexistent_header_with_iterable_default(self):
+        header = self.resp.getheader('No-Such-Header', ['default', 'values'])
+        self.assertEqual(header, 'default, values')
+
+        header = self.resp.getheader('No-Such-Header', ('default', 'values'))
+        self.assertEqual(header, 'default, values')
+
+    def test_getting_nonexistent_header_without_default(self):
+        header = self.resp.getheader('No-Such-Header')
+        self.assertEqual(header, None)
+
+
 def test_main(verbose=None):
     support.run_unittest(HeaderTests, OfflineTest, BasicTest, TimeoutTest,
-                         HTTPSTimeoutTest, RequestBodyTest, SourceAddressTest)
+                         HTTPSTimeoutTest, RequestBodyTest, SourceAddressTest,
+                         HTTPResponseTest)
 
 if __name__ == '__main__':
     test_main()