diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index 7f95181c67b509f406a4ab5e92ab379433e848d1..d24f8233a8157226627ac05f5ba81dcdb94f8d70 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -135,7 +135,7 @@ def calculate(operation, column_name, options = {})
     #   # SELECT people.id, people.name FROM people
     #   # => [[1, 'David'], [2, 'Jeremy'], [3, 'Jose']]
     #
-    #   Person.uniq.pluck(:role)
+    #   Person.pluck('DISTINCT role')
     #   # SELECT DISTINCT role FROM people
     #   # => ['admin', 'member', 'guest']
     #