--- a/Gemfile	Wed May 20 14:05:39 2020 +0900
+++ b/Gemfile	Wed Jul 08 11:08:19 2020 +0900
@@ -8,13 +8,18 @@
 #
 # This will help ensure the proper Jekyll version is running.
 # Happy Jekylling!
-gem "jekyll", "~> 3.8.6"
+
+# NOTE: Jekyll 4 released 2020-05-09, but no support for Pygments, see below
+#       https://jekyllrb.com/docs/liquid/tags/
+gem "jekyll", "~> 3.8.7" # Release 2020-05-08
 
 # If you have any plugins, put them here!
 group :jekyll_plugins do
-  gem "jekyll-feed", "~> 0.6"
+  gem "jekyll-feed", "~> 0.14" # Release 2020-06-24
 end
 
+# Rouge is the default highlighter for Jekyll 4 and does not support Octave
+# highlighting yet.  Thus stay on Jekyll 3.8 for a while.
 gem "pygments.rb"
 
 # Windows does not include zoneinfo files, so bundle the tzinfo-data gem