diff --git a/.rubocop_todo.yml b/.rubocop_todo.yml
index 5902525df..633278d00 100644
--- a/.rubocop_todo.yml
+++ b/.rubocop_todo.yml
@@ -47,14 +47,6 @@ Metrics/ModuleLength:
 Metrics/PerceivedComplexity:
   Max: 115
 
-# Offense count: 3
-# Cop supports --auto-correct.
-Performance/Casecmp:
-  Exclude:
-    - 'app/models/channel/email_parser.rb'
-    - 'app/models/channel/filter/database.rb'
-    - 'lib/tasks/zammad/setup/db_config.rake'
-
 # Offense count: 3
 # Cop supports --auto-correct.
 Rails/ApplicationRecord:
diff --git a/app/models/channel/email_parser.rb b/app/models/channel/email_parser.rb
index cc789e860..9852baf94 100644
--- a/app/models/channel/email_parser.rb
+++ b/app/models/channel/email_parser.rb
@@ -331,7 +331,7 @@ returns
     end
     return true if !class_name
 
-    if class_name.downcase == 'article'
+    if class_name.casecmp('article').zero?
       class_name = 'Ticket::Article'
     end
     return true if !attribute
diff --git a/app/models/channel/filter/database.rb b/app/models/channel/filter/database.rb
index 113b628de..4fa279e4b 100644
--- a/app/models/channel/filter/database.rb
+++ b/app/models/channel/filter/database.rb
@@ -48,7 +48,7 @@ module Channel::Filter::Database
 
         Rails.logger.info "  perform '#{key.downcase}' = '#{meta.inspect}'"
 
-        if key.downcase == 'x-zammad-ticket-tags' && meta['value'].present? && meta['operator'].present?
+        if key.casecmp('x-zammad-ticket-tags').zero? && meta['value'].present? && meta['operator'].present?
           mail[ 'x-zammad-ticket-tags'.downcase.to_sym ] ||= []
           tags = meta['value'].split(',')
 
diff --git a/lib/tasks/zammad/setup/db_config.rake b/lib/tasks/zammad/setup/db_config.rake
index 881c143bd..b24eea796 100644
--- a/lib/tasks/zammad/setup/db_config.rake
+++ b/lib/tasks/zammad/setup/db_config.rake
@@ -15,7 +15,7 @@ namespace :zammad do
         next if FileUtils.identical?(template, destination)
 
         printf 'config/database.yml: File exists. Overwrite? [y/N] '
-        next if STDIN.gets.chomp.downcase != 'y'
+        next if !STDIN.gets.chomp.casecmp('y').zero?
       end
 
       FileUtils.cp(template, destination)