diff --git a/ChangeLog b/ChangeLog
index e26449540a..bad1f25948 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Tue Jun  3 12:51:57 2008  Akinori MUSHA  <knu@iDaemons.org>
+
+	* enumerator.c (enumerator_allocate, enumerator_ptr): Properly
+	  detect if the object is initialized and raise error when
+	  appropriate.
+	  (enumerator_initialize): Fix a typo in rdoc. [ruby-core:17052]
+
 Tue Jun  3 01:21:51 2008  Yusuke Endoh  <mame@tsg.ne.jp>
 
 	* test/ruby/test_method.rb: add a test.
diff --git a/enumerator.c b/enumerator.c
index a930c2bfa6..0801517657 100644
--- a/enumerator.c
+++ b/enumerator.c
@@ -56,7 +56,7 @@ enumerator_ptr(VALUE obj)
 		 "wrong argument type %s (expected %s)",
 		 rb_obj_classname(obj), rb_class2name(rb_cEnumerator));
     }
-    if (!ptr) {
+    if (!ptr || ptr->obj == Qundef) {
 	rb_raise(rb_eArgError, "uninitialized enumerator");
     }
     return ptr;
@@ -204,8 +204,13 @@ static VALUE
 enumerator_allocate(VALUE klass)
 {
     struct enumerator *ptr;
-    return Data_Make_Struct(klass, struct enumerator,
-			    enumerator_mark, -1, ptr);
+    VALUE enum_obj;
+
+    enum_obj = Data_Make_Struct(klass, struct enumerator,
+				enumerator_mark, -1, ptr);
+    ptr->obj = Qundef;
+
+    return enum_obj;
 }
 
 static VALUE
@@ -217,7 +222,13 @@ enumerator_each_i(VALUE v, VALUE enum_obj, int argc, VALUE *argv)
 static VALUE
 enumerator_init(VALUE enum_obj, VALUE obj, VALUE meth, int argc, VALUE *argv)
 {
-    struct enumerator *ptr = enumerator_ptr(enum_obj);
+    struct enumerator *ptr;
+
+    Data_Get_Struct(enum_obj, struct enumerator, ptr);
+
+    if (!ptr) {
+	rb_raise(rb_eArgError, "unallocated enumerator");
+    }
 
     ptr->obj  = obj;
     ptr->meth = rb_to_id(meth);
@@ -237,8 +248,7 @@ enumerator_init(VALUE enum_obj, VALUE obj, VALUE meth, int argc, VALUE *argv)
  *  used as an Enumerable object using the given object's given
  *  method with the given arguments.
  *
- *  Use of this method is not discouraged.  Use Kernel#enum_for()
- *  instead.
+ *  Use of this method is discouraged.  Use Kernel#enum_for() instead.
  */
 static VALUE
 enumerator_initialize(int argc, VALUE *argv, VALUE obj)