diff --git a/activesupport/CHANGELOG b/activesupport/CHANGELOG
index 791a2f2712962da1bce1d75f4029fa9dc7ac9254..36db4dc6057afbaac4def3e42d08120e5df3fb29 100644
--- a/activesupport/CHANGELOG
+++ b/activesupport/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Enhance Inflector.underscore to convert '-' into '_' (as the inverse of Inflector.dasherize) [Jamis Buck]
+
 * Switched to_xml to use the xml schema format for datetimes.  This allows the encoding of time zones and should improve operability. [Koz]
 
 * Added a note to the documentation for the Date related Numeric extensions to indicate that they're
diff --git a/activesupport/lib/active_support/inflector.rb b/activesupport/lib/active_support/inflector.rb
index bbc5e10579237e46cdd08dd91ce3515edb03da5e..43620757c29ba23f7f76007ebceacccd246716c0 100644
--- a/activesupport/lib/active_support/inflector.rb
+++ b/activesupport/lib/active_support/inflector.rb
@@ -118,7 +118,11 @@ def titleize(word)
   end
   
   def underscore(camel_cased_word)
-    camel_cased_word.to_s.gsub(/::/, '/').gsub(/([A-Z]+)([A-Z][a-z])/,'\1_\2').gsub(/([a-z\d])([A-Z])/,'\1_\2').downcase
+    camel_cased_word.to_s.gsub(/::/, '/').
+      gsub(/([A-Z]+)([A-Z][a-z])/,'\1_\2').
+      gsub(/([a-z\d])([A-Z])/,'\1_\2').
+      tr("-", "_").
+      downcase
   end
   
   def dasherize(underscored_word)
diff --git a/activesupport/test/inflector_test.rb b/activesupport/test/inflector_test.rb
index d3f4a7727e0182846bf791691004c87095028e9a..12976a6d92ddcc0fce8f197793b61a16be0cfb5c 100644
--- a/activesupport/test/inflector_test.rb
+++ b/activesupport/test/inflector_test.rb
@@ -302,4 +302,10 @@ def test_dasherize
       assert_equal(dasherized, Inflector.dasherize(underscored))
     end
   end
+
+  def test_underscore_as_reverse_of_dasherize
+    UnderscoresToDashes.each do |underscored, dasherized|
+      assert_equal(underscored, Inflector.underscore(Inflector.dasherize(underscored)))
+    end
+  end
 end