diff --git a/.rubocop.yml b/.rubocop.yml
index b231624..1c0f832 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -8,6 +8,7 @@ Performance:
   Enabled: true
 
 AllCops:
+  TargetRubyVersion: 2.4
   Exclude:
     - 'vendor/bundle/**/*'
 
diff --git a/lib/liquid/file_system.rb b/lib/liquid/file_system.rb
index b2093ae..27ab632 100644
--- a/lib/liquid/file_system.rb
+++ b/lib/liquid/file_system.rb
@@ -59,7 +59,7 @@ module Liquid
     end
 
     def full_path(template_path)
-      raise FileSystemError, "Illegal template name '#{template_path}'" unless template_path =~ %r{\A[^./][a-zA-Z0-9_/]+\z}
+      raise FileSystemError, "Illegal template name '#{template_path}'" unless %r{\A[^./][a-zA-Z0-9_/]+\z}.match?(template_path)
 
       full_path = if template_path.include?('/')
         File.join(root, File.dirname(template_path), @pattern % File.basename(template_path))
diff --git a/lib/liquid/tags/raw.rb b/lib/liquid/tags/raw.rb
index 093a37e..fde3ee1 100644
--- a/lib/liquid/tags/raw.rb
+++ b/lib/liquid/tags/raw.rb
@@ -40,7 +40,7 @@ module Liquid
     protected
 
     def ensure_valid_markup(tag_name, markup, parse_context)
-      unless markup =~ Syntax
+      unless Syntax.match?(markup)
         raise SyntaxError, parse_context.locale.t("errors.syntax.tag_unexpected_args", tag: tag_name)
       end
     end
diff --git a/lib/liquid/utils.rb b/lib/liquid/utils.rb
index 406d667..709fb00 100644
--- a/lib/liquid/utils.rb
+++ b/lib/liquid/utils.rb
@@ -52,7 +52,7 @@ module Liquid
       when Numeric
         obj
       when String
-        obj.strip =~ /\A-?\d+\.\d+\z/ ? BigDecimal(obj) : obj.to_i
+        /\A-?\d+\.\d+\z/.match?(obj.strip) ? BigDecimal(obj) : obj.to_i
       else
         if obj.respond_to?(:to_number)
           obj.to_number