IPv6 is Off But Still Get Gateway Issue Log Entries

[NOYB]

Every 15 minutes:
Dec 30 18:30:30 php: : Could not find IPv6 gateway for interface(wan).
Dec 30 18:45:02 php: : Could not find IPv6 gateway for interface(wan).
Dec 30 19:00:03 php: : Could not find IPv6 gateway for interface(wan).

Both LAN & WAN have IPv6 Configuration Type set to None.

[NOYB]

Figured out the cause.  Had a firewall rule with IPv6 specified.