diff --git a/ChangeLog b/ChangeLog
index 90cc73873a..5cab630893 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Jan 12 00:36:29 2005  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* object.c (rb_class_superclass): superclass of singleton class also
+	  should be a singleton class.  fixed: [ruby-list:40519]
+
 Tue Jan 11 20:58:52 2005  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* io.c (remain_size): use buffered data instead of unreading to avoid
diff --git a/object.c b/object.c
index 308e1dc8d7..13f16b1c80 100644
--- a/object.c
+++ b/object.c
@@ -1587,6 +1587,9 @@ rb_class_superclass(klass)
     if (!super) {
 	rb_raise(rb_eTypeError, "uninitialized class");
     }
+    if (FL_TEST(klass, FL_SINGLETON)) {
+	super = RBASIC(klass)->klass;
+    }
     while (TYPE(super) == T_ICLASS) {
 	super = RCLASS(super)->super;
     }