diff --git a/Lib/asyncio/streams.py b/Lib/asyncio/streams.py
index 4517ca22d74637..177f7db75a4e1c 100644
--- a/Lib/asyncio/streams.py
+++ b/Lib/asyncio/streams.py
@@ -2,7 +2,7 @@
     'StreamReader', 'StreamWriter', 'StreamReaderProtocol',
     'open_connection', 'start_server')
 
-import collections
+import collections.abc
 import socket
 import sys
 import warnings
@@ -597,7 +597,7 @@ async def readuntil(self, separator=b'\n'):
         the shortest possible separator is considered to be the one that
         matched.
         """
-        if isinstance(separator, bytes):
+        if isinstance(separator, collections.abc.Buffer):
             separator = [separator]
         else:
             # Makes sure shortest matches wins, and supports arbitrary iterables
diff --git a/Lib/test/test_asyncio/test_streams.py b/Lib/test/test_asyncio/test_streams.py
index 792e88761acdc2..8af06a060cd4fb 100644
--- a/Lib/test/test_asyncio/test_streams.py
+++ b/Lib/test/test_asyncio/test_streams.py
@@ -512,6 +512,13 @@ def test_readuntil_multi_separator_negative_offset(self):
         self.assertEqual(b'dataZA', data)
         self.assertEqual(b'aaa', stream._buffer)
 
+    def test_readuntil_bytearray(self):
+        stream = asyncio.StreamReader(loop=self.loop)
+        stream.feed_data(b'some data\r\n')
+        data = self.loop.run_until_complete(stream.readuntil(bytearray(b'\r\n')))
+        self.assertEqual(b'some data\r\n', data)
+        self.assertEqual(b'', stream._buffer)
+
     def test_readexactly_zero_or_less(self):
         # Read exact number of bytes (zero or less).
         stream = asyncio.StreamReader(loop=self.loop)