diff --git a/activesupport/lib/active_support/core_ext/float.rb b/activesupport/lib/active_support/core_ext/float.rb
index 7570471b95..4f6f606680 100644
--- a/activesupport/lib/active_support/core_ext/float.rb
+++ b/activesupport/lib/active_support/core_ext/float.rb
@@ -1 +1 @@
-require 'active_support/core_ext/float/rounding'
+require 'active_support/core_ext/float/rounding' if RUBY_VERSION < '1.9'
diff --git a/railties/guides/source/active_support_core_extensions.textile b/railties/guides/source/active_support_core_extensions.textile
index 1df36137b4..39a87d9f64 100644
--- a/railties/guides/source/active_support_core_extensions.textile
+++ b/railties/guides/source/active_support_core_extensions.textile
@@ -1818,7 +1818,7 @@ h3. Extensions to +Float+
 
 h4. +round+
 
-The built-in method +Float#round+ rounds a float to the nearest integer. Active Support adds an optional parameter to let you specify a precision:
+The built-in method +Float#round+ rounds a float to the nearest integer. In Ruby 1.9 this method takes optional parameter to let you specify a precision. Active Support adds that functionality to +round+ in previous versions of Ruby:
 
 <ruby>
 Math::E.round(4) # => 2.7183