[TYPO3-calendar] Several errors in TYPO3 log (cal 1.11 + TYPO3 8.7)

[Markus]

Hello,
the TYPO3 error log is flooded with many error messages coming from cal 
like this:

Core: Error handler (BE): PHP Warning: Declaration of 
TYPO3\CMS\Cal\Model\ICalendar\vevent::parsevCalendar($data) should be 
compatible with TYPO3\CMS\Cal\Model\ICalendar::parsevCalendar($text, 
$base = 'VCALENDAR', $charset = 'utf8', $clear = true) in 
/..../typo3conf/ext/cal/Classes/Model/ICalendar/vevent.php line 223

Core: Error handler (BE): PHP Warning: Declaration of 
TYPO3\CMS\Cal\Model\ICalendar\vtimezone::parsevCalendar($data) should be 
compatible with TYPO3\CMS\Cal\Model\ICalendar::parsevCalendar($text, 
$base = 'VCALENDAR', $charset = 'utf8', $clear = true) in 
/....../typo3conf/ext/cal/Classes/Model/ICalendar/vtimezone.php line 160

Core: Error handler (BE): PHP Warning: Declaration of 
TYPO3\CMS\Cal\Model\ICalendar\valarm::parsevCalendar($data) should be 
compatible with TYPO3\CMS\Cal\Model\ICalendar::parsevCalendar($text, 
$base = 'VCALENDAR', $charset = 'utf8', $clear = true) in 
/...../typo3conf/ext/cal/Classes/Model/ICalendar/valarm.php line 27


Is it a bug / incompatibility with TYPO3 8.7?

Thx,
markus