diff --git a/flaschengeist/utils/datetime.py b/flaschengeist/utils/datetime.py
index eb2ba82..7c50c41 100644
--- a/flaschengeist/utils/datetime.py
+++ b/flaschengeist/utils/datetime.py
@@ -7,5 +7,5 @@ def from_iso_format(date_str):
     """Z-suffix aware version of `datetime.datetime.fromisoformat`"""
     time = datetime.datetime.fromisoformat(date_str.replace('Z', '+00:00'))
     if time.tzinfo:
-        return time.astimezone(tzinfo=datetime.timezone.utc)
+        return time.astimezone(datetime.timezone.utc)
     return time.replace(tzinfo=datetime.timezone.utc)