diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 830c72a6..b7ec0cf1 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -19,10 +19,8 @@ jobs:
           - ruby: truffleruby
           - ruby: truffleruby+graalvm
           - ruby: jruby
-          - ruby: "2.5"
-            rake_task: "rubocop test"
-          - ruby: "2.6"
           - ruby: "2.7"
+            rake_task: "rubocop test"
           - ruby: "3.0"
           - ruby: "3.1"
             coverage: "yes"
diff --git a/.rubocop.yml b/.rubocop.yml
index 82770e34..65de9ee5 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -6,7 +6,7 @@ require:
   - rubocop-rspec
   - rubocop-performance
 AllCops:
-  TargetRubyVersion: 2.5
+  TargetRubyVersion: 2.7
   NewCops: enable
 
 Style/TrailingCommaInHashLiteral:
diff --git a/json-schema.gemspec b/json-schema.gemspec
index bb54e590..8ad36d09 100644
--- a/json-schema.gemspec
+++ b/json-schema.gemspec
@@ -14,7 +14,7 @@ Gem::Specification.new do |s|
   s.files = Dir['lib/**/*', 'resources/*.json']
   s.require_path = 'lib'
   s.extra_rdoc_files = ['README.md', 'LICENSE.md']
-  s.required_ruby_version = '>= 2.5'
+  s.required_ruby_version = '>= 2.7'
   s.license = 'MIT'
   s.required_rubygems_version = '>= 2.5'
 
diff --git a/test/common_test_suite_test.rb b/test/common_test_suite_test.rb
index a6a2374f..9ceed574 100644
--- a/test/common_test_suite_test.rb
+++ b/test/common_test_suite_test.rb
@@ -26,7 +26,7 @@ def self.skip?(current_test, file_path)
     version = File.basename(suite).to_sym
     Dir["#{suite}/**/*.json"].each do |tfile|
       test_list = JSON.parse(File.read(tfile))
-      rel_file = tfile[TEST_DIR.length + 1..-1]
+      rel_file = tfile[TEST_DIR.length + 1..]
 
       test_list.each do |test|
         schema = test['schema']