diff --git a/.rubocop.yml b/.rubocop.yml
index dc42b75..62ba652 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -5,7 +5,7 @@ inherit_gem:
   rubocop-jekyll: .rubocop.yml
 
 AllCops:
-  TargetRubyVersion: 2.4
+  TargetRubyVersion: 2.3
   Exclude:
     - vendor/**/*
     - spec/*.rb
diff --git a/.rubocop_todo.yml b/.rubocop_todo.yml
index ccdfa8a..3db0a29 100644
--- a/.rubocop_todo.yml
+++ b/.rubocop_todo.yml
@@ -1,31 +1,21 @@
 # This configuration was generated by
 # `rubocop --auto-gen-config`
-# on 2018-10-26 17:08:37 +0200 using RuboCop version 0.60.0.
+# on 2019-07-16 18:09:04 +0200 using RuboCop version 0.71.0.
 # The point is for the user to remove these configuration records
 # one by one as the offenses are removed from the code base.
 # Note that changes in the inspected code, or installation of new
 # versions of RuboCop, may require this file to be generated again.
 
-# Offense count: 1
-Lint/IneffectiveAccessModifier:
-  Exclude:
-    - 'lib/jekyll-gist/gist_tag.rb'
-
 # Offense count: 1
 Lint/ShadowedException:
   Exclude:
     - 'lib/jekyll-gist/gist_tag.rb'
 
 # Offense count: 1
-# Configuration parameters: Max.
 Metrics/AbcSize:
-  Exclude:
-    - 'lib/jekyll-gist/gist_tag.rb'
+  Max: 24
 
 # Offense count: 1
-# Cop supports --auto-correct.
-# Configuration parameters: EnforcedStyle.
-# SupportedStyles: short, verbose
-Style/PreferredHashMethods:
-  Exclude:
-    - 'lib/jekyll-gist/gist_tag.rb'
+# Configuration parameters: CountComments, ExcludedMethods.
+Metrics/MethodLength:
+  Max: 21
diff --git a/.travis.yml b/.travis.yml
index b4f6166..5918f53 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,8 +1,8 @@
 language: ruby
 cache: bundler
 rvm:
-  - 2.6
-  - 2.4
+  - &latest_ruby 2.7
+  - 2.5
 
 script : script/cibuild
 
@@ -10,13 +10,15 @@ branches:
   only:
     - master
 env:
-  - JEKYLL_VERSION=3.7.4
-
+  matrix:
+  - JEKYLL_VERSION="~> 3.8"
 matrix:
   include:
     - # GitHub Pages
       rvm: 2.5.3
-      env: GH_PAGES=true
+      env: JEKYLL_VERSION="~> 3.8.5"
+    - rvm: *latest_ruby
+      env: JEKYLL_VERSION="~> 4.0"
 
 notifications:
   email: false
diff --git a/Gemfile b/Gemfile
index c24711a..46cdbf0 100644
--- a/Gemfile
+++ b/Gemfile
@@ -3,8 +3,4 @@
 source "https://rubygems.org"
 gemspec
 
-if ENV["GH_PAGES"]
-  gem "github-pages"
-elsif ENV["JEKYLL_VERSION"]
-  gem "jekyll", "~> #{ENV["JEKYLL_VERSION"]}"
-end
+gem "jekyll", ENV["JEKYLL_VERSION"] if ENV["JEKYLL_VERSION"]
diff --git a/History.markdown b/History.markdown
index b2ee842..a254054 100644
--- a/History.markdown
+++ b/History.markdown
@@ -1,15 +1,21 @@
-## 1.6.0 / 2019-03-22
+## HEAD
 
 ### Development Fixes
 
   * Test against Ruby 2.5 (#57)
   * Rely on rubocop-jekyll (#62)
   * chore(deps): rubocop-jekyll 0.3 (#64)
+  * Refactor GistTag (#65)
 
 ### Major Enhancements
 
   * chore(deps): drop support for Liquid < 4.0 (#66)
 
+### Bug Fixes
+
+  * Re-introduce Ruby 2.3 support and test Jekyll 3.7+ (#72)
+  * Use Liquid::Tag#raw to clarify error message (#73)
+
 ## 1.5.0 / 2017-12-03
 
 ### Documentation
diff --git a/jekyll-gist.gemspec b/jekyll-gist.gemspec
index 81f8e22..ba7a55e 100644
--- a/jekyll-gist.gemspec
+++ b/jekyll-gist.gemspec
@@ -1,9 +1,6 @@
 # frozen_string_literal: true
 
-lib = File.expand_path("lib", __dir__)
-
-$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
-require "jekyll-gist/version"
+require_relative "lib/jekyll-gist/version"
 
 Gem::Specification.new do |spec|
   spec.name          = "jekyll-gist"
@@ -14,16 +11,16 @@ Gem::Specification.new do |spec|
   spec.homepage      = "https://github.com/jekyll/jekyll-gist"
   spec.license       = "MIT"
 
-  spec.required_ruby_version = ">= 2.4.0"
-
   spec.files         = `git ls-files -z`.split("\x0")
-  spec.executables   = spec.files.grep(%r!^bin/!) { |f| File.basename(f) }
-  spec.test_files    = spec.files.grep(%r!^(test|spec|features)/!)
+  spec.test_files    = spec.files.grep(%r!^spec/!)
   spec.require_paths = ["lib"]
 
-  spec.add_dependency "octokit", "~> 4.2"
+  spec.required_ruby_version = ">= 2.3.0"
+
+  spec.add_runtime_dependency "jekyll", ">= 3.7", "< 5.0"
+  spec.add_runtime_dependency "octokit", "~> 4.2"
+
   spec.add_development_dependency "bundler"
-  spec.add_development_dependency "jekyll", ">= 3.7", "< 5.0"
   spec.add_development_dependency "rake"
   spec.add_development_dependency "rspec"
   spec.add_development_dependency "rubocop-jekyll", "~> 0.4"
diff --git a/lib/jekyll-gist/gist_tag.rb b/lib/jekyll-gist/gist_tag.rb
index 2633692..ae8ae34 100644
--- a/lib/jekyll-gist/gist_tag.rb
+++ b/lib/jekyll-gist/gist_tag.rb
@@ -10,22 +10,30 @@
 module Jekyll
   module Gist
     class GistTag < Liquid::Tag
+      def self.client
+        @client ||= Octokit::Client.new :access_token => ENV["JEKYLL_GITHUB_TOKEN"]
+      end
+
       def render(context)
         @encoding = context.registers[:site].config["encoding"] || "utf-8"
         @settings = context.registers[:site].config["gist"]
         if (tag_contents = determine_arguments(@markup.strip))
-          gist_id = tag_contents[0]
+          gist_id  = tag_contents[0]
           filename = tag_contents[1]
-          gist_id = context[gist_id] if context_contains_key?(context, gist_id)
-          filename = context[filename] if context_contains_key?(context, filename)
+          gist_id  = context[gist_id]  if context.key?(gist_id)
+          filename = context[filename] if context.key?(filename)
+
           noscript_tag = gist_noscript_tag(gist_id, filename)
-          script_tag = gist_script_tag(gist_id, filename)
+          script_tag   = gist_script_tag(gist_id, filename)
+
           "#{noscript_tag}#{script_tag}"
         else
           raise ArgumentError, <<~ERROR
             Syntax error in tag 'gist' while parsing the following markup:
-             #{@markup}
-             Valid syntax:
+
+              '{% #{raw.strip} %}'
+
+            Valid syntax:
               {% gist user/1234567 %}
               {% gist user/1234567 foo.js %}
               {% gist 28949e1d5ee2273f9fd3 %}
@@ -42,17 +50,10 @@ def determine_arguments(input)
         [matched[1].strip, matched[2].strip] if matched && matched.length >= 3
       end
 
-      def context_contains_key?(context, key)
-        if context.respond_to?(:has_key?)
-          context.has_key?(key)
-        else
-          context.key?(key)
-        end
-      end
-
       def gist_script_tag(gist_id, filename = nil)
         url = "https://gist.github.com/#{gist_id}.js"
         url = "#{url}?file=#{filename}" unless filename.to_s.empty?
+
         "<script src=\"#{url}\"> </script>"
       end
 
@@ -60,18 +61,14 @@ def gist_noscript_tag(gist_id, filename = nil)
         return if @settings && @settings["noscript"] == false
 
         code = fetch_raw_code(gist_id, filename)
-        if !code.nil?
+        if code
           code = code.force_encoding(@encoding)
-          code = CGI.escapeHTML(code)
-
-          # CGI.escapeHTML behavior differs in Ruby < 2.0
-          # See https://github.com/jekyll/jekyll-gist/pull/28
-          code = code.gsub("'", "&#39;") if RUBY_VERSION < "2.0"
+          code = CGI.escapeHTML(code).gsub("'", "&#39;")
 
           "<noscript><pre>#{code}</pre></noscript>"
         else
-          Jekyll.logger.warn "Warning:", "The <noscript> tag for your gist #{gist_id} "
-          Jekyll.logger.warn "", "could not be generated. This will affect users who do "
+          Jekyll.logger.warn "Warning:", "The <noscript> tag for your gist #{gist_id}"
+          Jekyll.logger.warn "", "could not be generated. This will affect users who do"
           Jekyll.logger.warn "", "not have JavaScript enabled in their browsers."
         end
       end
@@ -82,6 +79,7 @@ def fetch_raw_code(gist_id, filename = nil)
         url = "https://gist.githubusercontent.com/#{gist_id}/raw"
         url = "#{url}/#{filename}" unless filename.to_s.empty?
         uri = URI(url)
+
         Net::HTTP.start(uri.host, uri.port,
                         :use_ssl => uri.scheme == "https",
                         :read_timeout => 3, :open_timeout => 3) do |http|
@@ -95,7 +93,6 @@ def fetch_raw_code(gist_id, filename = nil)
 
       def code_from_api(gist_id, filename = nil)
         gist = GistTag.client.gist gist_id
-
         file = if filename.to_s.empty?
                  # No file specified, return the value of the first key/value pair
                  gist.files.first[1]
@@ -109,10 +106,6 @@ def code_from_api(gist_id, filename = nil)
 
         file[:content] if file
       end
-
-      def self.client
-        @client ||= Octokit::Client.new :access_token => ENV["JEKYLL_GITHUB_TOKEN"]
-      end
     end
   end
 end
diff --git a/lib/jekyll-gist/version.rb b/lib/jekyll-gist/version.rb
index ca4dd69..2bef474 100644
--- a/lib/jekyll-gist/version.rb
+++ b/lib/jekyll-gist/version.rb
@@ -2,6 +2,6 @@
 
 module Jekyll
   module Gist
-    VERSION = "1.6.0"
+    VERSION = "1.5.0"
   end
 end
diff --git a/spec/gist_tag_spec.rb b/spec/gist_tag_spec.rb
index f04618c..b889220 100644
--- a/spec/gist_tag_spec.rb
+++ b/spec/gist_tag_spec.rb
@@ -168,7 +168,7 @@
       let(:gist) { "" }
 
       it "raises an error" do
-        expect(-> { output }).to raise_error
+        expect(-> { output }).to raise_error(ArgumentError)
       end
     end
   end

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