diff --git a/Gemfile b/Gemfile
index cc91aef..0350b57 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 source "https://rubygems.org"
 
 gemspec
diff --git a/Rakefile b/Rakefile
index 3cc7987..24e7bde 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #--
 # Copyright (C) 2015 SUSE LLC
 #   This library is free software; you can redistribute it and/or modify
diff --git a/lib/libyui/rake.rb b/lib/libyui/rake.rb
index ff5e29e..6809278 100644
--- a/lib/libyui/rake.rb
+++ b/lib/libyui/rake.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #--
 # Copyright (C) 2015 SUSE LLC
 #   This library is free software; you can redistribute it and/or modify
@@ -23,7 +25,7 @@
   include Libyui::Tasks::Helpers
 
   # read package name from spec file name because CWD can have a -branch suffix
-  main_spec = Dir.glob("package/*.spec").sort.last
+  main_spec = Dir.glob("package/*.spec").max
   conf.package_name = main_spec[/package\/(.*)\.spec$/, 1]
 
   conf.version = cmake_version
diff --git a/lib/libyui/tasks.rb b/lib/libyui/tasks.rb
index 0c2c791..2cac04c 100644
--- a/lib/libyui/tasks.rb
+++ b/lib/libyui/tasks.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #--
 # Copyright (C) 2015-2021 SUSE LLC
 #   This library is free software; you can redistribute it and/or modify
@@ -19,7 +21,7 @@ module Libyui
   # Facilities to write Libyui related rake tasks.
   module Tasks
     # Name of the CMake version file
-    VERSION_CMAKE = "VERSION.cmake".freeze
+    VERSION_CMAKE = "VERSION.cmake"
     # Targets definition
     TARGETS_FILE = File.expand_path("../../data/targets.yml", __dir__)
 
@@ -145,7 +147,7 @@ def bump_spec_so_version(filename = nil)
       # @param filename [String, nil] if nil, it uses the shortest spec filename
       # @return [String]
       def spec_filename(filename)
-        filename || Dir.glob("package/*.spec").sort.first
+        filename || Dir.glob("package/*.spec").min
       end
     end
   end
diff --git a/lib/tasks/so_version.rake b/lib/tasks/so_version.rake
index 2f34244..2dbe0f4 100644
--- a/lib/tasks/so_version.rake
+++ b/lib/tasks/so_version.rake
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #--
 # Copyright (C) 2021 SUSE LLC
 #   This library is free software; you can redistribute it and/or modify
@@ -24,7 +26,7 @@ namespace :so_version do
     filenames = Dir.glob("package/*.spec").sort
     filenames.reject! { |f| spec_so_version(f).nil? }
 
-    mismatches = filenames.select { |f| spec_so_version(f) != so_version }
+    mismatches = filenames.reject { |f| spec_so_version(f) == so_version }
 
     if mismatches.any?
       messages = ["so version mismatch:"]
diff --git a/lib/tasks/test.rake b/lib/tasks/test.rake
index 3d339a4..6a7b57a 100644
--- a/lib/tasks/test.rake
+++ b/lib/tasks/test.rake
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #--
 # Copyright (C) 2015 SUSE LLC
 #   This library is free software; you can redistribute it and/or modify
diff --git a/lib/tasks/version.rake b/lib/tasks/version.rake
index a8a8a3c..ac26b59 100644
--- a/lib/tasks/version.rake
+++ b/lib/tasks/version.rake
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #--
 # Copyright (C) 2015 SUSE LLC
 #   This library is free software; you can redistribute it and/or modify
diff --git a/libyui-rake.gemspec b/libyui-rake.gemspec
index b678775..d904f34 100644
--- a/libyui-rake.gemspec
+++ b/libyui-rake.gemspec
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #--
 # Copyright (C) 2015 SUSE LLC
 #   This library is free software; you can redistribute it and/or modify