diff --git a/Gemfile b/Gemfile
index 37f5eaa4..1ece4c01 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,2 +1,10 @@
+# frozen_string_literal: true
+
 source 'https://rubygems.org'
+
+git_source(:github) {|repo_name| "https://github.com/#{repo_name}" }
+
+# Synchronize with https://pages.github.com/versions
+ruby '>=2.5.3'
+
 gem 'github-pages', group: :jekyll_plugins