Ubuntu – dpkg warning about ‘/etc/lsb-release’ version number not starting with a digit

I believe I spotted it during the upgrade from Ubuntu GNOME 15.10 to 16.04, but I know for sure that I spotted it just know during a dist-upgrade, I sometimes get this warning from dpkg:

dpkg: warning: version '/etc/lsb-release' has bad syntax: version number does not start with a digit

The contents of the /etc/lsb-release file is:

DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=16.04
DISTRIB_CODENAME=xenial
DISTRIB_DESCRIPTION="Ubuntu 16.04 LTS"

So I'm not entirely sure what the problem is and what (if anything) I should do about it… Is this a bug in the lsb-release file (somewhere where I haven't noticed) or is this a problem with dpkg or…?