diff --git a/ChangeLog b/ChangeLog
index 0e7e46dea3..f3c0702485 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+Wed Jun 18 12:05:30 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* marshal.c (w_object, marshal_dump, r_object0, marshal_load): search
+	  public methods only.  [ruby-core:17283]
+
+	* object.c (convert_type): ditto.
+
+	* lib/singleton.rb (Singleton#_dump): conversion method should be
+	  public.
+
 Wed Jun 18 10:18:11 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* ext/etc/etc.c (etc_passwd, etc_group): fixed rdoc.  a patch from
diff --git a/lib/singleton.rb b/lib/singleton.rb
index a5c7eb164d..c6a2527d9a 100644
--- a/lib/singleton.rb
+++ b/lib/singleton.rb
@@ -71,8 +71,6 @@ module Singleton
     raise TypeError, "can't dup instance of singleton #{self.class}"
   end
 
-  private
-
   #  default marshalling strategy
   def _dump(depth = -1)
     ''
diff --git a/marshal.c b/marshal.c
index 692b37de93..c9170c6f37 100644
--- a/marshal.c
+++ b/marshal.c
@@ -582,7 +582,7 @@ w_object(VALUE obj, struct dump_arg *arg, int limit)
     else {
 	if (OBJ_TAINTED(obj)) arg->taint = Qtrue;
 
-	if (rb_obj_respond_to(obj, s_mdump, Qtrue)) {
+	if (rb_respond_to(obj, s_mdump)) {
 	    volatile VALUE v;
 
             st_add_direct(arg->data, obj, arg->data->num_entries);
@@ -594,7 +594,7 @@ w_object(VALUE obj, struct dump_arg *arg, int limit)
 	    if (hasiv) w_ivar(obj, 0, &c_arg);
 	    return;
 	}
-	if (rb_obj_respond_to(obj, s_dump, Qtrue)) {
+	if (rb_respond_to(obj, s_dump)) {
 	    VALUE v;
             st_table *ivtbl2 = 0;
             int hasiv2;
@@ -759,7 +759,7 @@ w_object(VALUE obj, struct dump_arg *arg, int limit)
 	    {
 		VALUE v;
 
-		if (!rb_obj_respond_to(obj, s_dump_data, Qtrue)) {
+		if (!rb_respond_to(obj, s_dump_data)) {
 		    rb_raise(rb_eTypeError,
 			     "no marshal_dump is defined for class %s",
 			     rb_obj_classname(obj));
@@ -856,13 +856,13 @@ marshal_dump(int argc, VALUE *argv)
     }
     arg.dest = 0;
     if (!NIL_P(port)) {
-	if (!rb_obj_respond_to(port, s_write, Qtrue)) {
+	if (!rb_respond_to(port, s_write)) {
 	  type_error:
 	    rb_raise(rb_eTypeError, "instance of IO needed");
 	}
 	arg.str = rb_str_buf_new(0);
 	arg.dest = port;
-	if (rb_obj_respond_to(port, s_binmode, Qtrue)) {
+	if (rb_respond_to(port, s_binmode)) {
 	    rb_funcall2(port, s_binmode, 0, 0);
 	}
     }
@@ -1420,7 +1420,7 @@ r_object0(struct load_arg *arg, int *ivp, VALUE extmod)
 	    VALUE klass = path2class(r_unique(arg));
 	    VALUE data;
 
-	    if (!rb_obj_respond_to(klass, s_load, Qtrue)) {
+	    if (!rb_respond_to(klass, s_load)) {
 		rb_raise(rb_eTypeError, "class %s needs to have method `_load'",
 			 rb_class2name(klass));
 	    }
@@ -1448,7 +1448,7 @@ r_object0(struct load_arg *arg, int *ivp, VALUE extmod)
                     rb_extend_object(v, m);
                 }
             }
-	    if (!rb_obj_respond_to(v, s_mload, Qtrue)) {
+	    if (!rb_respond_to(v, s_mload)) {
 		rb_raise(rb_eTypeError, "instance of %s needs to have method `marshal_load'",
 			 rb_class2name(klass));
 	    }
@@ -1475,7 +1475,7 @@ r_object0(struct load_arg *arg, int *ivp, VALUE extmod)
       case TYPE_DATA:
        {
            VALUE klass = path2class(r_unique(arg));
-           if (rb_obj_respond_to(klass, s_alloc, Qtrue)) {
+           if (rb_respond_to(klass, s_alloc)) {
 	       static int warn = Qtrue;
 	       if (warn) {
 		   rb_warn("define `allocate' instead of `_alloc'");
@@ -1491,7 +1491,7 @@ r_object0(struct load_arg *arg, int *ivp, VALUE extmod)
                rb_raise(rb_eArgError, "dump format error");
            }
            v = r_entry(v, arg);
-           if (!rb_obj_respond_to(v, s_load_data, Qtrue)) {
+           if (!rb_respond_to(v, s_load_data)) {
                rb_raise(rb_eTypeError,
                         "class %s needs to have instance method `_load_data'",
                         rb_class2name(klass));
@@ -1596,8 +1596,8 @@ marshal_load(int argc, VALUE *argv)
 	arg.taint = OBJ_TAINTED(port); /* original taintedness */
 	port = v;
     }
-    else if (rb_obj_respond_to(port, s_getbyte, Qtrue) && rb_obj_respond_to(port, s_read, Qtrue)) {
-	if (rb_obj_respond_to(port, s_binmode, Qtrue)) {
+    else if (rb_respond_to(port, s_getbyte) && rb_respond_to(port, s_read)) {
+	if (rb_respond_to(port, s_binmode)) {
 	    rb_funcall2(port, s_binmode, 0, 0);
 	}
 	arg.taint = Qtrue;
diff --git a/object.c b/object.c
index 0d18ea5b29..e4f513763e 100644
--- a/object.c
+++ b/object.c
@@ -1904,7 +1904,7 @@ convert_type(VALUE val, const char *tname, const char *method, int raise)
     ID m;
 
     m = rb_intern(method);
-    if (!rb_obj_respond_to(val, m, Qtrue)) {
+    if (!rb_respond_to(val, m)) {
 	if (raise) {
 	    rb_raise(rb_eTypeError, "can't convert %s into %s",
 		     NIL_P(val) ? "nil" :