diff --git a/colorls.gemspec b/colorls.gemspec
index 578739c..5b3c7b0 100644
--- a/colorls.gemspec
+++ b/colorls.gemspec
@@ -29,7 +29,7 @@ POST_INSTALL_MESSAGE = %(
 Gem::Specification.new do |spec|
   is_tagged = ENV['GITHUB_REF'] == "refs/tags/v#{ColorLS::VERSION}"
   is_origin = ENV['GITHUB_REPOSITORY_OWNER'] == 'athityakumar'
-  build_number = ENV['GITHUB_RUN_NUMBER']
+  build_number = ENV.fetch('GITHUB_RUN_NUMBER', nil)
 
   spec.name          = 'colorls'
   spec.version       = if build_number && is_origin && !is_tagged
@@ -76,11 +76,12 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'ronn', '~> 0'
   spec.add_development_dependency 'rspec', '~> 3.7'
   spec.add_development_dependency 'rspec-its', '~> 1.2'
-  spec.add_development_dependency 'rubocop', '~> 1.22.0'
+  spec.add_development_dependency 'rubocop', '~> 1.29.1'
   spec.add_development_dependency 'rubocop-performance', '~> 1.13.0'
   spec.add_development_dependency 'rubocop-rake', '~> 0.5'
   spec.add_development_dependency 'rubocop-rspec', '~> 2.10.0'
   spec.add_development_dependency 'rubygems-tasks', '~> 0'
   spec.add_development_dependency 'simplecov', '~> 0.21.2'
+  spec.metadata['rubygems_mfa_required'] = 'true'
 end
 # rubocop:enable Metrics/BlockLength
diff --git a/lib/colorls/flags.rb b/lib/colorls/flags.rb
index f37d6ce..d80c245 100644
--- a/lib/colorls/flags.rb
+++ b/lib/colorls/flags.rb
@@ -2,7 +2,6 @@
 
 require 'optparse'
 require 'colorls/version'
-require 'ostruct'
 
 module ColorLS
   class Flags
@@ -31,6 +30,8 @@ module ColorLS
       process_args
     end
 
+    Option = Struct.new(:flags, :desc)
+
     def options
       list = @parser.top.list + @parser.base.list
 
@@ -40,7 +41,7 @@ module ColorLS
         flags = o.short + o.long
         next if flags.empty?
 
-        OpenStruct.new(flags: flags, desc: o.desc)
+        Option.new(flags, o.desc)
       end
 
       result.compact
diff --git a/spec/color_ls/core_spec.rb b/spec/color_ls/core_spec.rb
index 8a7c512..6cce9dd 100644
--- a/spec/color_ls/core_spec.rb
+++ b/spec/color_ls/core_spec.rb
@@ -25,12 +25,11 @@ RSpec.describe ColorLS::Core do
         chardev?: false,
         socket?: false,
         symlink?: false,
-        stats: OpenStruct.new(
-          mode: 0o444, # read for user, owner, other
-          setuid?: false,
-          setgid?: false,
-          sticky?: false
-        ),
+        stats: instance_double(File::Stat,
+                               mode: 0o444, # read for user, owner, other
+                               setuid?: false,
+                               setgid?: false,
+                               sticky?: false),
         executable?: true
       )
 
@@ -48,12 +47,11 @@ RSpec.describe ColorLS::Core do
         chardev?: false,
         socket?: false,
         symlink?: false,
-        stats: OpenStruct.new(
-          mode: 0o444, # read for user, owner, other
-          setuid?: false,
-          setgid?: false,
-          sticky?: false
-        ),
+        stats: instance_double(File::Stat,
+                               mode: 0o444, # read for user, owner, other
+                               setuid?: false,
+                               setgid?: false,
+                               sticky?: false),
         executable?: false
       )
 
diff --git a/spec/color_ls/flags_spec.rb b/spec/color_ls/flags_spec.rb
index 12cb4fa..33d3c92 100644
--- a/spec/color_ls/flags_spec.rb
+++ b/spec/color_ls/flags_spec.rb
@@ -88,12 +88,11 @@ RSpec.describe ColorLS::Flags do
         chardev?: false,
         socket?: false,
         symlink?: false,
-        stats: OpenStruct.new(
-          mode: 0o444, # read for user, owner, other
-          setuid?: true,
-          setgid?: true,
-          sticky?: true
-        ),
+        stats: instance_double(File::Stat,
+                               mode: 0o444, # read for user, owner, other
+                               setuid?: true,
+                               setgid?: true,
+                               sticky?: true),
         executable?: false
       )
 
@@ -122,12 +121,11 @@ RSpec.describe ColorLS::Flags do
         chardev?: false,
         socket?: false,
         symlink?: false,
-        stats: OpenStruct.new(
-          mode: 0o444, # read for user, owner, other
-          setuid?: true,
-          setgid?: true,
-          sticky?: true
-        ),
+        stats: instance_double(File::Stat,
+                               mode: 0o444, # read for user, owner, other
+                               setuid?: true,
+                               setgid?: true,
+                               sticky?: true),
         executable?: false
       )
 
@@ -409,12 +407,11 @@ RSpec.describe ColorLS::Flags do
         chardev?: false,
         socket?: false,
         symlink?: false,
-        stats: OpenStruct.new(
-          mode: 0o444, # read for user, owner, other
-          setuid?: true,
-          setgid?: true,
-          sticky?: true
-        ),
+        stats: instance_double(File::Stat,
+                               mode: 0o444, # read for user, owner, other
+                               setuid?: true,
+                               setgid?: true,
+                               sticky?: true),
         executable?: false
       )
 
@@ -453,12 +450,11 @@ RSpec.describe ColorLS::Flags do
         chardev?: false,
         socket?: false,
         symlink?: false,
-        stats: OpenStruct.new(
-          mode: 0o444, # read for user, owner, other
-          setuid?: true,
-          setgid?: true,
-          sticky?: true
-        ),
+        stats: instance_double(File::Stat,
+                               mode: 0o444, # read for user, owner, other
+                               setuid?: true,
+                               setgid?: true,
+                               sticky?: true),
         executable?: false
       )
 
@@ -497,12 +493,11 @@ RSpec.describe ColorLS::Flags do
         chardev?: false,
         socket?: false,
         symlink?: false,
-        stats: OpenStruct.new(
-          mode: 0o444, # read for user, owner, other
-          setuid?: true,
-          setgid?: true,
-          sticky?: true
-        ),
+        stats: instance_double(File::Stat,
+                               mode: 0o444, # read for user, owner, other
+                               setuid?: true,
+                               setgid?: true,
+                               sticky?: true),
         executable?: false
       )
 
@@ -541,12 +536,11 @@ RSpec.describe ColorLS::Flags do
         chardev?: false,
         socket?: false,
         symlink?: false,
-        stats: OpenStruct.new(
-          mode: 0o444, # read for user, owner, other
-          setuid?: true,
-          setgid?: true,
-          sticky?: true
-        ),
+        stats: instance_double(File::Stat,
+                               mode: 0o444, # read for user, owner, other
+                               setuid?: true,
+                               setgid?: true,
+                               sticky?: true),
         executable?: false
       )
 
@@ -599,12 +593,11 @@ RSpec.describe ColorLS::Flags do
         chardev?: false,
         socket?: false,
         symlink?: false,
-        stats: OpenStruct.new(
-          mode: 0o444, # read for user, owner, other
-          setuid?: true,
-          setgid?: true,
-          sticky?: true
-        ),
+        stats: instance_double(File::Stat,
+                               mode: 0o444, # read for user, owner, other
+                               setuid?: true,
+                               setgid?: true,
+                               sticky?: true),
         executable?: false
       )