diff --git a/ChangeLog b/ChangeLog
index 47dac08bf1..c097d0f89f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Wed Sep 22 00:52:44 2010  WATANABE Hirofumi  <eban@ruby-lang.org>
+
+	* lib/rdoc/ri/store.rb (save_cache): remove duplicate entries.
+
 Wed Sep 22 00:00:05 2010  Tanaka Akira  <akr@fsij.org>
 
 	* ext/pathname/pathname.c (path_f_pathname): Pathname() translated
diff --git a/lib/rdoc/ri/store.rb b/lib/rdoc/ri/store.rb
index 81ffb7e674..db02202f81 100644
--- a/lib/rdoc/ri/store.rb
+++ b/lib/rdoc/ri/store.rb
@@ -172,9 +172,11 @@ class RDoc::RI::Store
 
   def save_cache
     # HACK mongrel-1.1.5 documents its files twice
+    @cache[:ancestors].       each do |_, m| m.uniq!; m.sort! end
     @cache[:attributes].      each do |_, m| m.uniq!; m.sort! end
     @cache[:class_methods].   each do |_, m| m.uniq!; m.sort! end
     @cache[:instance_methods].each do |_, m| m.uniq!; m.sort! end
+    @cache[:modules].uniq!; @cache[:modules].sort!
 
     open cache_path, 'wb' do |io|
       Marshal.dump @cache, io