diff --git a/radicale/__init__.py b/radicale/__init__.py
index 9894d9f..17866f7 100644
--- a/radicale/__init__.py
+++ b/radicale/__init__.py
@@ -30,6 +30,7 @@ import os
 import pprint
 import base64
 import socket
+import socketserver
 import ssl
 import wsgiref.simple_server
 import re
@@ -92,6 +93,14 @@ class HTTPSServer(HTTPServer):
         self.server_activate()
 
 
+class ThreadedHTTPServer(socketserver.ThreadingMixIn, HTTPServer):
+    pass
+
+
+class ThreadedHTTPSServer(socketserver.ThreadingMixIn, HTTPSServer):
+    pass
+
+
 class RequestHandler(wsgiref.simple_server.WSGIRequestHandler):
     """HTTP requests handler."""
     def log_message(self, *args, **kwargs):
diff --git a/radicale/__main__.py b/radicale/__main__.py
index 73f7f2b..c60b834 100644
--- a/radicale/__main__.py
+++ b/radicale/__main__.py
@@ -33,7 +33,8 @@ import ssl
 from wsgiref.simple_server import make_server
 
 from . import (
-    Application, config, HTTPServer, HTTPSServer, log, RequestHandler, VERSION)
+    Application, config, ThreadedHTTPServer, ThreadedHTTPSServer, log,
+    RequestHandler, VERSION)
 
 
 # This is a script, many branches and variables
@@ -152,7 +153,7 @@ def run():
     # Create collection servers
     servers = {}
     if configuration.getboolean("server", "ssl"):
-        server_class = HTTPSServer
+        server_class = ThreadedHTTPSServer
         server_class.certificate = configuration.get("server", "certificate")
         server_class.key = configuration.get("server", "key")
         server_class.cyphers = configuration.get("server", "cyphers")
@@ -168,7 +169,7 @@ def run():
                     "Error while reading SSL %s %r: %s" % (
                         name, filename, exception))
     else:
-        server_class = HTTPServer
+        server_class = ThreadedHTTPServer
 
     if not configuration.getboolean("server", "dns_lookup"):
         RequestHandler.address_string = lambda self: self.client_address[0]