diff --git a/ChangeLog b/ChangeLog
index d772b35df7..dd13d84548 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Wed Sep 16 13:15:17 2009  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* template/Doxyfile.tmpl: RbConfig::CONFIG['DOT'] is sometimes nil.
+
 Wed Sep 16 10:14:54 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* README.EXT, README.EXT.ja (rb_protect, rb_jump_tag): added.
diff --git a/template/Doxyfile.tmpl b/template/Doxyfile.tmpl
index 0fd9462c69..34a42983ce 100644
--- a/template/Doxyfile.tmpl
+++ b/template/Doxyfile.tmpl
@@ -12,7 +12,7 @@ unless miniruby
   miniruby = './miniruby$(EXEEXT) -I$(srcdir)/lib -I$(EXTOUT)/common -I./- -r$(srcdir)/ext/purelib.rb'
   RbConfig.expand(miniruby, RbConfig::CONFIG.merge("srcdir"=>srcdir))
 end
-dot = RbConfig::CONFIG['DOT']
+dot = RbConfig::CONFIG['DOT'] || ""
 have_dot = dot.empty? ? "NO" : "YES"
 %>
 #---------------------------------------------------------------------------