--- requirements.txt.orig	2024-07-04 13:11:39 UTC
+++ requirements.txt
@@ -1,7 +1,7 @@
 # install requirements depending on python version
 # see https://www.python.org/dev/peps/pep-0508/#environment-markers
 
-icalendar >= 5.0.0, < 7.0.0
+icalendar >= 4.0.0, < 7.0.0
 python-dateutil >= 2.8.1, < 3.0.0
 x-wr-timezone == 0.*
 backports.zoneinfo; python_version == "3.7" or python_version == "3.8"
