diff --git a/activesupport/lib/active_support/cache.rb b/activesupport/lib/active_support/cache.rb
index 6062776ec35..186e3da52e9 100644
--- a/activesupport/lib/active_support/cache.rb
+++ b/activesupport/lib/active_support/cache.rb
@@ -394,6 +394,7 @@ module ActiveSupport
       #
       # ==== Options
       #
+      # * +:namespace+ - Replace the store namespace for this call.
       # * +:version+ - Specifies a version for the cache entry. If the cached
       #   version does not match the requested version, the read will be treated
       #   as a cache miss. This feature is used to support recyclable cache keys.