jekyll 3.2.1 | Error: Liquid syntax error (line 56): Unknown tag 'last_modified_at'

[juanpabloaj]

When I run

jekyll serve

I get this message

jekyll 3.2.1 | Error:  Liquid syntax error (line 56): Unknown tag 'last_modified_at'

I installed jekyll-last-modified-at with

gem install jekyll-last-modified-at

[zx1986]

Did you try add gem 'jekyll-last-modified-at' to a Gemfile in the same directory, then bundle ?

source 'https://rubygems.org'

gem 'jekyll'
gem 'jekyll-last-modified-at'

Then:

bundle install
bundle exec jekyll server

[Messjer]

I put group: :jekyll_plugins in Gemfile and it works for me.

#Gemfile
gem "jekyll-last-modified-at", group: :jekyll_plugins

[gjtorikian]

README has been updated with this info, sorry for the trouble.