diff --git a/activesupport/lib/active_support/inflections.rb b/activesupport/lib/active_support/inflections.rb
index f0e6449ceb..100ad411c3 100644
--- a/activesupport/lib/active_support/inflections.rb
+++ b/activesupport/lib/active_support/inflections.rb
@@ -45,6 +45,7 @@
   inflect.irregular 'person', 'people'
   inflect.irregular 'man', 'men'
   inflect.irregular 'child', 'children'
+  inflect.irregular 'sex', 'sexes'
 
   inflect.uncountable %w( equipment information rice money species series fish sheep )
 end
\ No newline at end of file