Tags links returning a 404

[rk295]

I've noticed the links to the tag page return a 404, the rendered link is (in this example) tags/elasticsearch which is a directory and does exist, but it only contains the xml file. The actual list page is elasticsearch.html in the root of the tags directory:

% ls -ld ela* ; ls -l elasticsearch
drwxr-xr-x  3 robin  staff     96 31 Aug 11:17 elasticsearch
-rw-r--r--  1 robin  staff  35044 31 Aug 11:17 elasticsearch.html
total 16
-rw-r--r--  1 robin  staff  4099 31 Aug 11:17 index.xml

Changing the link in tags.html to be:

  <a class="tag-link" href="{{ "/tags/" | relLangURL }}{{ . | urlize }}.html">{{ . }}</a>

fixes the problem. Is this a bug with my config or the theme?

Hugo version hugo v0.87.0+extended darwin/amd64 BuildDate=unknown.