diff --git a/ChangeLog b/ChangeLog
index 9a639f3153..514fb2ce0c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,4 +1,9 @@
-Wed Apr  3 16:34:24 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+Wed Apr  3 16:35:32 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* bignum.c (rb_big_eq): hide intermediate Bignums not just freeing
+	  memory.  [ruby-core:53893] [Bug #8204]
+
+	* object.c (rb_obj_hide): hide an object by clearing klass.
 
 	* bignum.c (rb_big_eq): test as Fixnum if possible and get rid of zero
 	  length Bignum.  [ruby-core:53893] [Bug #8204]
diff --git a/bignum.c b/bignum.c
index 6d2b25f997..b2daac75af 100644
--- a/bignum.c
+++ b/bignum.c
@@ -1095,6 +1095,8 @@ big2str_karatsuba(VALUE x, int base, char* ptr,
 
     b = power_cache_get_power(base, n1, &m1);
     bigdivmod(x, b, &q, &r);
+    rb_obj_hide(q);
+    rb_obj_hide(r);
     lh = big2str_karatsuba(q, base, ptr, (len - m1)/2,
 			   len - m1, hbase, trim);
     rb_big_resize(q, 0);
diff --git a/internal.h b/internal.h
index 6cb6b91589..b19d321086 100644
--- a/internal.h
+++ b/internal.h
@@ -196,6 +196,7 @@ VALUE rb_int_pred(VALUE num);
 
 /* object.c */
 VALUE rb_obj_equal(VALUE obj1, VALUE obj2);
+VALUE rb_obj_hide(VALUE obj);
 
 /* parse.y */
 VALUE rb_parser_get_yydebug(VALUE);
diff --git a/object.c b/object.c
index 94acf1721c..72de18f7ef 100644
--- a/object.c
+++ b/object.c
@@ -43,6 +43,15 @@ static ID id_const_missing;
     (!SPECIAL_CONST_P(obj) && \
      (BUILTIN_TYPE(obj) == T_CLASS || BUILTIN_TYPE(obj) == T_MODULE))
 
+VALUE
+rb_obj_hide(VALUE obj)
+{
+    if (!SPECIAL_CONST_P(obj)) {
+	RBASIC(obj)->klass = 0;
+    }
+    return obj;
+}
+
 /*
  *  call-seq:
  *     obj === other   -> true or false