diff --git a/ChangeLog b/ChangeLog
index dc53386cc2..cf82d4fb51 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Apr 12 18:07:13 2011  TAKAO Kouji  <kouji@takao7.net>
+
+	* ext/readline/extconf.rb: --disable-libedit to disable
+	  libedit. fixes #4550
+
 Tue Apr 12 10:37:39 2011  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* include/ruby/win32.h: VC doesn't have ftruncate() and others, but
diff --git a/ext/readline/extconf.rb b/ext/readline/extconf.rb
index 59c2a8e95d..685da8c5bf 100644
--- a/ext/readline/extconf.rb
+++ b/ext/readline/extconf.rb
@@ -34,12 +34,19 @@ have_library("ncurses", "tgetnum") ||
   have_library("termcap", "tgetnum") ||
   have_library("curses", "tgetnum")
 
-if enable_libedit
+case enable_libedit
+when true
   unless (have_readline_header("editline/readline.h") ||
           have_readline_header("readline/readline.h")) &&
           have_library("edit", "readline")
     exit
   end
+when nil
+  unless ((have_readline_header("readline/readline.h") &&
+           have_readline_header("readline/history.h")) &&
+           have_library("readline", "readline"))
+    exit
+  end
 else
   unless ((have_readline_header("readline/readline.h") &&
            have_readline_header("readline/history.h")) &&