diff --git a/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb b/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb
index e4bfd9f7c5025a8a18afdd203e107a2dcd73b55d..9525c10112a98fc1c0f41e03dfb709d0a54e45cc 100644
--- a/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb
@@ -48,7 +48,7 @@ def future?
 
     # Returns true if the date/time falls on a Saturday or Sunday.
     def on_weekend?
-      wday.in?(WEEKEND_DAYS)
+      WEEKEND_DAYS.include?(wday)
     end
 
     # Returns a new date/time the specified number of days ago.