diff --git a/.rubocop.yml b/.rubocop.yml
index 9f3c016..717c0e3 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -1,5 +1,5 @@
 AllCops:
-  TargetRubyVersion: 2.4
+  TargetRubyVersion: 2.6
   DisplayCopNames: true
 
 Layout/HashAlignment:
@@ -24,9 +24,6 @@ Style/UnpackFirst:
 # Lint
 #
 
-Lint/SuppressedException:
-  Enabled: false
-
 Lint/Loop:
   Enabled: false
 
@@ -35,6 +32,13 @@ Lint/RaiseException:
 
 Lint/StructNewOverride:
   Enabled: false
+
+Lint/SuppressedException:
+  Enabled: false
+
+Lint/UselessAssignment:
+  Enabled: false
+
 #
 # Metrics
 #
@@ -49,13 +53,13 @@ Metrics/BlockLength:
 Metrics/ClassLength:
   Max: 128
 
+Metrics/CyclomaticComplexity:
+  Max: 15
+
 Metrics/MethodLength:
   CountComments: false
   Max: 50
 
-Metrics/CyclomaticComplexity:
-  Max: 15
-
 Metrics/PerceivedComplexity:
   Max: 15
 
@@ -63,6 +67,9 @@ Metrics/PerceivedComplexity:
 # Style
 #
 
+Style/AsciiComments:
+  Enabled: false
+
 Style/ExponentialNotation:
   Enabled: false
 
diff --git a/lib/nio.rb b/lib/nio.rb
index bca3ee6..a232626 100644
--- a/lib/nio.rb
+++ b/lib/nio.rb
@@ -29,7 +29,7 @@ def self.pure?(env = ENV)
     end
 
     # Native Ruby on Windows is not supported:
-    if (Gem.win_platform? && !defined?(JRUBY_VERSION))
+    if Gem.win_platform? && !defined?(JRUBY_VERSION)
       return true
     end
 
@@ -38,7 +38,7 @@ def self.pure?(env = ENV)
     #   return true
     # end
 
-    return false
+    false
   end
 end
 
diff --git a/nio4r.gemspec b/nio4r.gemspec
index cd05d76..59a9603 100644
--- a/nio4r.gemspec
+++ b/nio4r.gemspec
@@ -7,12 +7,14 @@ Gem::Specification.new do |spec|
   spec.version = NIO::VERSION
 
   spec.summary = "New IO for Ruby"
+  # rubocop:disable Layout/LineLength
   spec.authors = ["Tony Arcieri", "Samuel Williams", "Olle Jonsson", "Gregory Longtin", "Tiago Cardoso", "Joao Fernandes", "Thomas Dziedzic", "Boaz Segev", "Logan Bowers", "Pedro Paiva", "Jun Aruga", "Omer Katz", "Upekshe Jayasekera", "Tim Carey-Smith", "Benoit Daloze", "Sergey Avseyev", "Tomoya Ishida", "Usaku Nakamura", "Cédric Boutillier", "Daniel Berger", "Dirkjan Bussink", "Hiroshi Shibata", "Jesús Burgos Maciá", "Luis Lavena", "Pavel Rosický", "Sadayuki Furuhashi", "Stephen von Takach", "Vladimir Kochnev", "Vít Ondruch", "Anatol Pomozov", "Bernd Ahlers", "Charles Oliver Nutter", "Denis Washington", "Elad Eyal", "Jean byroot Boussier", "Jeffrey Martin", "John Thornton", "Jun Jiang", "Lars Kanis", "Marek Kowalcze", "Maxime Demolin", "Orien Madgwick", "Pavel Lobashov", "Per Lundberg", "Phillip Aldridge", "Ravil Bayramgalin", "Shannon Skipper", "Tao Luo", "Thomas Kuntz", "Tsimnuj Hawj", "Zhang Kang"]
+  # rubocop:enable Layout/LineLength
   spec.licenses = ["MIT", "BSD-2-Clause"]
 
   unless defined? JRUBY_VERSION
-    spec.cert_chain  = ['release.cert']
-    spec.signing_key = File.expand_path('~/.gem/release.pem')
+    spec.cert_chain  = ["release.cert"]
+    spec.signing_key = File.expand_path("~/.gem/release.pem")
   end
 
   spec.homepage = "https://github.com/socketry/nio4r"
@@ -23,11 +25,11 @@ Gem::Specification.new do |spec|
     "documentation_uri" => "https://www.rubydoc.info/gems/nio4r",
     "funding_uri" => "https://github.com/sponsors/ioquatix/",
     "source_code_uri" => "https://github.com/socketry/nio4r.git",
-    "wiki_uri" => "https://github.com/socketry/nio4r/wiki",
+    "wiki_uri" => "https://github.com/socketry/nio4r/wiki"
   }
 
-  spec.files = Dir.glob(['{ext,lib}/**/*', '*.md'], File::FNM_DOTMATCH, base: __dir__)
-  spec.require_paths = ['lib']
+  spec.files = Dir.glob(["{ext,lib}/**/*", "*.md"], File::FNM_DOTMATCH, base: __dir__)
+  spec.require_paths = ["lib"]
 
   spec.required_ruby_version = ">= 2.6"
 
diff --git a/rakelib/extension.rake b/rakelib/extension.rake
index 47fddf0..8388ea6 100644
--- a/rakelib/extension.rake
+++ b/rakelib/extension.rake
@@ -4,7 +4,7 @@ if defined? JRUBY_VERSION
   require "rake/javaextensiontask"
   Rake::JavaExtensionTask.new("nio4r_ext") do |ext|
     ext.ext_dir = "ext/nio4r"
-    ext.release = '8'
+    ext.release = "8"
   end
 else
   require "rake/extensiontask"
diff --git a/readme.md b/readme.md
index 1c52891..95e877d 100644
--- a/readme.md
+++ b/readme.md
@@ -27,7 +27,6 @@ writing.
 
 ## Supported platforms
 
-  - Ruby 2.5
   - Ruby 2.6
   - Ruby 2.7
   - Ruby 3.0
diff --git a/spec/nio/selectables/tcp_socket_spec.rb b/spec/nio/selectables/tcp_socket_spec.rb
index 1d93b20..8b41c6a 100644
--- a/spec/nio/selectables/tcp_socket_spec.rb
+++ b/spec/nio/selectables/tcp_socket_spec.rb
@@ -84,25 +84,23 @@
     include_context NIO::Selector
 
     it "selects writable when connected" do
-      begin
-        server = TCPServer.new(addr, 0)
+      server = TCPServer.new(addr, 0)
 
-        client = Socket.new(Socket::AF_INET, Socket::SOCK_STREAM, 0)
-        monitor = selector.register(client, :w)
+      client = Socket.new(Socket::AF_INET, Socket::SOCK_STREAM, 0)
+      monitor = selector.register(client, :w)
 
-        expect do
-          client.connect_nonblock server.local_address
-        end.to raise_exception Errno::EINPROGRESS
+      expect do
+        client.connect_nonblock server.local_address
+      end.to raise_exception Errno::EINPROGRESS
 
-        ready = selector.select(1)
+      ready = selector.select(1)
 
-        expect(ready).to include monitor
-        result = client.getsockopt(::Socket::SOL_SOCKET, ::Socket::SO_ERROR)
-        expect(result.unpack("i").first).to be_zero
-      ensure
-        server.close rescue nil
-        selector.close rescue nil
-      end
+      expect(ready).to include monitor
+      result = client.getsockopt(::Socket::SOL_SOCKET, ::Socket::SO_ERROR)
+      expect(result.unpack("i").first).to be_zero
+    ensure
+      server.close rescue nil
+      selector.close rescue nil
     end
   end
 end