diff --git a/ChangeLog b/ChangeLog
index 94769a1306..f6ef4af7e8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sat Jul  7 21:59:29 2007  Tanaka Akira  <akr@fsij.org>
+
+	* lib/pp.rb (PP::PPMethods#pp_hash): sort condition changed:
+	  all keys have a same class which is kind of Comparable.
+
 Sat Jul  7 17:12:37 2007  Koichi Sasada  <ko1@atdot.net>
 
 	* compile.c: use rb_bug() instead of rb_compile_error().
diff --git a/lib/pp.rb b/lib/pp.rb
index e92ab014a7..53ecaedd59 100644
--- a/lib/pp.rb
+++ b/lib/pp.rb
@@ -248,10 +248,11 @@ class PP < PrettyPrint
     def pp_hash(obj)
       group(1, '{', '}') {
         keys = obj.keys
-        if keys.all? {|k| k.respond_to? :to_str } ||
-           keys.all? {|k| k.is_a? Symbol } ||
-           keys.all? {|k| k.is_a? Integer }
-          keys.sort!
+        if 0 < keys.length
+          key_class = keys[0].class
+          if key_class < Comparable && keys.all? {|k| k.class == key_class }
+            keys.sort!
+          end
         end
         seplist(keys, nil, :each) {|k|
           v = obj[k]