Bind error: zone example.com/IN: NS 'ns1.example.com' has no address records (A or AAAA)

While checking the logs of my server, I ran into the following errors:

May 11 18:00:04 named[31875]: zone example.com/IN: NS 'ns1.example.com' has no address records (A or AAAA)
May 11 18:00:04 named[31875]: zone example.com/IN: NS 'ns2.example.com' has no address records (A or AAAA)
May 11 18:00:04 named[31875]: zone example.com/IN: NS 'ns3.example.com' has no address records (A or AAAA)

I ran into the same errors when I checked the zone files themselves using:
named-checkzone example.com /etc/bind/zones/example.com. So it appeared to be a syntax error. However, with other zone files on the server validating fine, it seemed that the issue was particular to the example.com zone file alone.

Comparing the problematic zone file against a healthy one highlighted the discrepancy. The domains of the nameservers in the example.com zone files were not terminated with a period (unlike the rest of the domain names in the file). Once this was fixed, all was peachy once again. The zone file validated successfully and my logs are bereft of these errors!

I hope this helps somebody out there :)