diff --git a/Lib/test/test_wsgiref.py b/Lib/test/test_wsgiref.py
index 213c5cf3b8a..544e42be494 100755
--- a/Lib/test/test_wsgiref.py
+++ b/Lib/test/test_wsgiref.py
@@ -7,7 +7,7 @@ from wsgiref import util
 from wsgiref.validate import validator
 from wsgiref.simple_server import WSGIServer, WSGIRequestHandler, demo_app
 from wsgiref.simple_server import make_server
-from StringIO import StringIO
+from io import StringIO, BytesIO
 from SocketServer import BaseServer
 import re, sys
 
@@ -47,9 +47,9 @@ def hello_app(environ,start_response):
     ])
     return ["Hello, world!"]
 
-def run_amock(app=hello_app, data="GET / HTTP/1.0\n\n"):
+def run_amock(app=hello_app, data=b"GET / HTTP/1.0\n\n"):
     server = make_server("", 80, app, MockServer, MockHandler)
-    inp, out, err, olderr = StringIO(data), StringIO(), StringIO(), sys.stderr
+    inp, out, err, olderr = BytesIO(data), StringIO(), StringIO(), sys.stderr
     sys.stderr = err
 
     try:
diff --git a/Lib/wsgiref/simple_server.py b/Lib/wsgiref/simple_server.py
index abb3620510a..980f97ab376 100644
--- a/Lib/wsgiref/simple_server.py
+++ b/Lib/wsgiref/simple_server.py
@@ -163,7 +163,7 @@ class WSGIRequestHandler(BaseHTTPRequestHandler):
 
 
 def demo_app(environ,start_response):
-    from StringIO import StringIO
+    from io import StringIO
     stdout = StringIO()
     print("Hello world!", file=stdout)
     print(file=stdout)
diff --git a/Lib/wsgiref/util.py b/Lib/wsgiref/util.py
index 5b44eda16df..a4ca02f91b8 100644
--- a/Lib/wsgiref/util.py
+++ b/Lib/wsgiref/util.py
@@ -149,7 +149,7 @@ def setup_testing_defaults(environ):
     environ.setdefault('wsgi.multithread', 0)
     environ.setdefault('wsgi.multiprocess', 0)
 
-    from StringIO import StringIO
+    from io import StringIO
     environ.setdefault('wsgi.input', StringIO(""))
     environ.setdefault('wsgi.errors', StringIO())
     environ.setdefault('wsgi.url_scheme',guess_scheme(environ))