logrotate: error creating output file /var/log/nagios3/nagios.log.1: File exists

while testing a merge req that lets nagios log to syslog i encountered an error that i see from time to time (for different logfiles though):

root@donkey:~# logrotate -d -f /etc/logrotate.d/nagios 
reading config file /etc/logrotate.d/nagios

Handling 1 logs

rotating pattern: /var/log/nagios3/nagios.log  forced from command line (5 rotations)
empty log files are not rotated, old logs are removed
considering log /var/log/nagios3/nagios.log
  log needs rotating
rotating log /var/log/nagios3/nagios.log, log->rotateCount is 5
dateext suffix '-20160929'
glob pattern '-[0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]'
renaming /var/log/nagios3/nagios.log.5.gz to /var/log/nagios3/nagios.log.6.gz (rotatecount 5, logstart 1, i 5), 
renaming /var/log/nagios3/nagios.log.4.gz to /var/log/nagios3/nagios.log.5.gz (rotatecount 5, logstart 1, i 4), 
renaming /var/log/nagios3/nagios.log.3.gz to /var/log/nagios3/nagios.log.4.gz (rotatecount 5, logstart 1, i 3), 
renaming /var/log/nagios3/nagios.log.2.gz to /var/log/nagios3/nagios.log.3.gz (rotatecount 5, logstart 1, i 2), 
renaming /var/log/nagios3/nagios.log.1.gz to /var/log/nagios3/nagios.log.2.gz (rotatecount 5, logstart 1, i 1), 
renaming /var/log/nagios3/nagios.log.0.gz to /var/log/nagios3/nagios.log.1.gz (rotatecount 5, logstart 1, i 0), 
copying /var/log/nagios3/nagios.log to /var/log/nagios3/nagios.log.1
truncating /var/log/nagios3/nagios.log
compressing log with: /bin/gzip
removing old log /var/log/nagios3/nagios.log.6.gz
error: error opening /var/log/nagios3/nagios.log.6.gz: No such file or directory
root@donkey:~# logrotate -f /etc/logrotate.d/nagios 
error: error creating output file /var/log/nagios3/nagios.log.1: File exists

manually removing this file fixes the problem:

rm /var/log/nagios3/nagios.log.1

I'm using leap::logfile to set up logrotation, and this is the logrotate snippet it produces:

root@donkey:~# cat /etc/logrotate.d/nagios 
/var/log/nagios3/nagios.log {
	rotate 5
	daily
	compress
	missingok
	notifempty
	copytruncate
}

(from redmine: created on 2016-09-29)