diff --git a/authserv/app_nginx.py b/authserv/app_nginx.py
index 653b25544ab0ab5c467c702d87f13fb173b297f0..923bb5cdc90c199ad17b0feec2bb770a4b6bc160 100644
--- a/authserv/app_nginx.py
+++ b/authserv/app_nginx.py
@@ -1,5 +1,5 @@
-import gevent.lock
 import socket
+import threading
 import urllib
 from flask import Flask, request, abort, make_response
 from authserv.app_common import do_auth
@@ -9,7 +9,7 @@ app = Flask(__name__)
 _default_port_map = {'imap': 143, 'pop3': 110}
 
 _dns_cache = {}
-_dns_cache_lock = gevent.lock.Semaphore()
+_dns_cache_lock = threading.Lock()
 
 def _shard_to_ip(shard):
     hostname = '%s-vpn' % shard