diff --git a/ChangeLog b/ChangeLog
index 786ab971b0..064154cffa 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Oct 24 18:49:16 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* ext/objspace/objspace.c (type2sym, count_objects_size): use enum
+	  instead of size_t which may be larger than actual values.
+
 Wed Oct 24 17:41:24 2012  Koichi Sasada  <ko1@atdot.net>
 
 	* benchmark/driver.rb: add `-x' or `--exclude' option
diff --git a/ext/objspace/objspace.c b/ext/objspace/objspace.c
index 41abed90f4..1889f11382 100644
--- a/ext/objspace/objspace.c
+++ b/ext/objspace/objspace.c
@@ -271,7 +271,7 @@ cos_i(void *vstart, void *vend, size_t stride, void *data)
 }
 
 static VALUE
-type2sym(int i)
+type2sym(enum ruby_value_type i)
 {
     VALUE type;
     switch (i) {
@@ -335,7 +335,7 @@ count_objects_size(int argc, VALUE *argv, VALUE os)
 {
     size_t counts[T_MASK+1];
     size_t total = 0;
-    size_t i;
+    enum ruby_value_type i;
     VALUE hash;
 
     if (rb_scan_args(argc, argv, "01", &hash) == 1) {