diff --git a/requirements.txt b/requirements.txt
index 01f948b..10e103d 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,5 @@
 O365>=2.1.4
 BeautifulSoup4>=4.13.3
-portalocker>=3.2.0
+portalocker>=4.0.0
 ical>=10.0.0
 oauthlib