diff --git a/fail2ban/server/iso8601.py b/fail2ban/server/iso8601.py
index a53557fb..a28ce13b 100644
--- a/fail2ban/server/iso8601.py
+++ b/fail2ban/server/iso8601.py
@@ -41,7 +41,7 @@ __all__ = ["parse_date", "ParseError"]
 # Adapted from http://delete.me.uk/2005/03/iso8601.html
 ISO8601_REGEX_RAW = "(?P<year>[0-9]{4})-(?P<month>[0-9]{1,2})-(?P<day>[0-9]{1,2})" \
     "T(?P<hour>[0-9]{2}):(?P<minute>[0-9]{2})(:(?P<second>[0-9]{2})(\.(?P<fraction>[0-9]+))?)?" \
-    "(?P<timezone>Z|(([-+])([0-9]{2}):([0-9]{2})))?"
+    "(?P<timezone>Z|[-+][0-9]{2}(:?[0-9]{2})?)?"
 ISO8601_REGEX = re.compile(ISO8601_REGEX_RAW)
 TIMEZONE_REGEX = re.compile("(?P<prefix>[+-])(?P<hours>[0-9]{2}):?(?P<minutes>[0-9]{2})?")