diff --git a/CHANGELOG.rdoc b/CHANGELOG.rdoc
index 5c7dd1b..d147b31 100644
--- a/CHANGELOG.rdoc
+++ b/CHANGELOG.rdoc
@@ -1,3 +1,8 @@
+Wed Feb 15 11:49:41 2012  Aaron Patterson <aaron@tenderlovemaking.com>
+
+	* lib/journey/formatter.rb: reject non-truthy parameters parts.
+          Fixes rails ticket #4587
+
 Mon Jan 23 17:07:53 2012  Aaron Patterson <aaron@tenderlovemaking.com>
 
 	* Added symbol? and literal? predicate methods to the ast nodes for
diff --git a/lib/journey/formatter.rb b/lib/journey/formatter.rb
index 7a84a8b..c7daceb 100644
--- a/lib/journey/formatter.rb
+++ b/lib/journey/formatter.rb
@@ -104,7 +104,7 @@ def verify_required_parts! route, parts
         if tests.key? key
           /\A#{tests[key]}\Z/ === parts[key]
         else
-          true
+          parts.fetch(key) { false }
         end
       }
     end