diff --git a/ChangeLog b/ChangeLog
index 38385a1b60..815d8aa611 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Nov 20 01:39:02 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* lib/rdoc/constant.rb (RDoc::Constant#documented?): workaround for
+	  NoMethodError when the original of alias is not found.
+
 Wed Nov 20 01:27:33 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* lib/delegate.rb (Delegator#send): separate from method_missing so
diff --git a/lib/rdoc/constant.rb b/lib/rdoc/constant.rb
index 48b32aaf98..97985cbf99 100644
--- a/lib/rdoc/constant.rb
+++ b/lib/rdoc/constant.rb
@@ -63,7 +63,15 @@ class RDoc::Constant < RDoc::CodeObject
   # for a documented class or module.
 
   def documented?
-    super or is_alias_for && is_alias_for.documented?
+    return true if super
+    return false unless @is_alias_for
+    case @is_alias_for
+    when String then
+      found = @store.find_class_or_module @is_alias_for
+      return false unless found
+      @is_alias_for = found
+    end
+    @is_alias_for.documented?
   end
 
   ##