diff --git a/pyproject.toml b/pyproject.toml
index ff25dca..030cc91 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -5,7 +5,7 @@ build-backend = "setuptools.build_meta"
 [project]
 name = "yaml2ics"
 version = "0.3rc1.dev0"
-requires-python = ">=3.8"
+requires-python = ">=3.9"
 authors = [{name = "Scientific Python Developers"}]
 readme = "README.md"
 license = {file = "LICENSE"}
diff --git a/tests/test_cli.py b/tests/test_cli.py
index f57e055..f4bbe9e 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -1,9 +1,9 @@
 import datetime
 import io
 import os
+import zoneinfo
 
 import pytest
-import zoneinfo
 
 from yaml2ics import event_from_yaml, files_to_events, main
 
diff --git a/yaml2ics.py b/yaml2ics.py
index 2227f1d..28b76be 100644
--- a/yaml2ics.py
+++ b/yaml2ics.py
@@ -8,12 +8,12 @@
 import datetime
 import os
 import sys
+import zoneinfo
 
 import dateutil
 import dateutil.rrule
 import ics
 import yaml
-import zoneinfo
 from dateutil.tz import gettz as _gettz
 
 interval_type = {
@@ -70,6 +70,7 @@ def event_from_yaml(event_yaml: dict, tz: datetime.tzinfo = None) -> ics.Event:
 
     if tz is None:
         tz = dateutil.tz.UTC
+
     if "timezone" in d:
         tzname = d.pop("timezone")
         tz = gettz(tzname)
@@ -95,6 +96,9 @@ def event_from_yaml(event_yaml: dict, tz: datetime.tzinfo = None) -> ics.Event:
     # or it was inferred from event start time.
     tz = event.timespan.begin_time.tzinfo
 
+    if not tz:
+        tz = dateutil.tz.UTC
+
     # Handle all-day events
     if not ("duration" in d or "end" in d):
         event.make_all_day()