Cron runs only once instead every minute

I'm trying to run a script every minute (on a Docker container running Ubuntu 16.04).

The /etc/echo.sh simply echo the word "hi"

cat /etc/crontab
* * * * *  root /etc/echo.sh > /var/log/cron.log 2>&1


/etc/init.d/cron reload
 * Reloading configuration files for periodic command scheduler cron     [ OK ]

tail -f /var/log/cron.log
hi

After printing "hi" once, nothing happens anymore.

Any ideas why?

The script does run every minute but > truncates the file each time.

If the file does not exist, it shall be created; otherwise, it shall be truncated to be an empty file after being opened.

^(source)

Use >> instead to append to the file.