diff --git a/swift/common/wsgi.py b/swift/common/wsgi.py
index 6f0f600f54..5e8d0311ae 100644
--- a/swift/common/wsgi.py
+++ b/swift/common/wsgi.py
@@ -35,7 +35,8 @@ from six import StringIO
 
 from swift.common import utils, constraints
 from swift.common.storage_policy import BindPortsCache
-from swift.common.swob import Request, wsgi_unquote
+from swift.common.swob import Request, wsgi_quote, wsgi_unquote, \
+    wsgi_quote_plus, wsgi_unquote_plus, wsgi_to_bytes, bytes_to_wsgi
 from swift.common.utils import capture_stdio, disable_fallocate, \
     drop_privileges, get_logger, NullLogger, config_true_value, \
     validate_configuration, get_hub, config_auto_int_value, \
@@ -433,6 +434,36 @@ class SwiftHttpProtocol(wsgi.HttpProtocol):
             '''If the client didn't provide a content type, leave it blank.'''
             return ''
 
+    def parse_request(self):
+        if not six.PY2:
+            # request lines *should* be ascii per the RFC, but historically
+            # we've allowed (and even have func tests that use) arbitrary
+            # bytes. This breaks on py3 (see https://bugs.python.org/issue33973
+            # ) but the work-around is simple: munge the request line to be
+            # properly quoted. py2 will do the right thing without this, but it
+            # doesn't hurt to re-write the request line like this and it
+            # simplifies testing.
+            if self.raw_requestline.count(b' ') >= 2:
+                parts = self.raw_requestline.split(b' ', 2)
+                path, q, query = parts[1].partition(b'?')
+                # unquote first, so we don't over-quote something
+                # that was *correctly* quoted
+                path = wsgi_to_bytes(wsgi_quote(wsgi_unquote(
+                    bytes_to_wsgi(path))))
+                query = b'&'.join(
+                    sep.join([
+                        wsgi_to_bytes(wsgi_quote_plus(wsgi_unquote_plus(
+                            bytes_to_wsgi(key)))),
+                        wsgi_to_bytes(wsgi_quote_plus(wsgi_unquote_plus(
+                            bytes_to_wsgi(val))))
+                    ])
+                    for part in query.split(b'&')
+                    for key, sep, val in (part.partition(b'='), ))
+                parts[1] = path + q + query
+                self.raw_requestline = b' '.join(parts)
+            # else, mangled protocol, most likely; let base class deal with it
+        return wsgi.HttpProtocol.parse_request(self)
+
 
 class SwiftHttpProxiedProtocol(SwiftHttpProtocol):
     """
diff --git a/test/unit/common/test_wsgi.py b/test/unit/common/test_wsgi.py
index 26ce8092c0..d99877cc3b 100644
--- a/test/unit/common/test_wsgi.py
+++ b/test/unit/common/test_wsgi.py
@@ -27,6 +27,7 @@ import types
 
 import eventlet.wsgi
 
+import six
 from six import BytesIO
 from six.moves.urllib.parse import quote
 
@@ -984,11 +985,6 @@ class TestWSGI(unittest.TestCase):
 
 
 class TestSwiftHttpProtocol(unittest.TestCase):
-    def setUp(self):
-        patcher = mock.patch('swift.common.wsgi.wsgi.HttpProtocol')
-        self.mock_super = patcher.start()
-        self.addCleanup(patcher.stop)
-
     def _proto_obj(self):
         # Make an object we can exercise... note the base class's __init__()
         # does a bunch of work, so we just new up an object like eventlet.wsgi
@@ -1041,12 +1037,38 @@ class TestSwiftHttpProtocol(unittest.TestCase):
 
         self.assertEqual(False, proto_obj.parse_request())
 
-        self.assertEqual([], self.mock_super.mock_calls)
         self.assertEqual([
             mock.call(400, "Bad HTTP/0.9 request type ('jimmy')"),
         ], proto_obj.send_error.mock_calls)
         self.assertEqual(('a', '123'), proto_obj.client_address)
 
+    def test_request_line_cleanup(self):
+        def do_test(line_from_socket, expected_line=None):
+            if expected_line is None:
+                expected_line = line_from_socket
+
+            proto_obj = self._proto_obj()
+            proto_obj.raw_requestline = line_from_socket
+            with mock.patch('swift.common.wsgi.wsgi.HttpProtocol') \
+                    as mock_super:
+                proto_obj.parse_request()
+
+            self.assertEqual([mock.call.parse_request(proto_obj)],
+                             mock_super.mock_calls)
+            self.assertEqual(proto_obj.raw_requestline, expected_line)
+
+        do_test(b'GET / HTTP/1.1')
+        do_test(b'GET /%FF HTTP/1.1')
+
+        if not six.PY2:
+            do_test(b'GET /\xff HTTP/1.1', b'GET /%FF HTTP/1.1')
+            do_test(b'PUT /Here%20Is%20A%20SnowMan:\xe2\x98\x83 HTTP/1.0',
+                    b'PUT /Here%20Is%20A%20SnowMan%3A%E2%98%83 HTTP/1.0')
+            do_test(
+                b'POST /?and%20it=fixes+params&'
+                b'PALMTREE=\xf0%9f\x8c%b4 HTTP/1.1',
+                b'POST /?and+it=fixes+params&PALMTREE=%F0%9F%8C%B4 HTTP/1.1')
+
 
 class TestProxyProtocol(unittest.TestCase):
     def _run_bytes_through_protocol(self, bytes_from_client, protocol_class):