diff --git a/ChangeLog b/ChangeLog
index 009b45b740..d11099fb07 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,4 +1,7 @@
-Sun Aug 10 08:15:05 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+Sun Aug 10 08:56:14 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* gc.c (STACK_LEVEL_MAX, ruby_stack_length): returns size_t.
+	  [ruby-core:18207]
 
 	* configure.in (rb_cv_missing__dtos18, rb_cv_missing_fconvert),
 	  ext/digest/md5/md5.c, ext/openssl/ossl.c (main),
diff --git a/gc.c b/gc.c
index d6919422a4..e408570ad3 100644
--- a/gc.c
+++ b/gc.c
@@ -815,7 +815,7 @@ ruby_get_stack_grow_direction(VALUE *addr)
 
 #define GC_WATER_MARK 512
 
-int
+size_t
 ruby_stack_length(VALUE **p)
 {
     rb_thread_t *th = GET_THREAD();
diff --git a/include/ruby/intern.h b/include/ruby/intern.h
index 243e7015a0..acd8d84c6b 100644
--- a/include/ruby/intern.h
+++ b/include/ruby/intern.h
@@ -330,7 +330,7 @@ VALUE rb_file_directory_p(VALUE,VALUE);
 void ruby_set_stack_size(size_t);
 NORETURN(void rb_memerror(void));
 int ruby_stack_check(void);
-int ruby_stack_length(VALUE**);
+size_t ruby_stack_length(VALUE**);
 int rb_during_gc(void);
 void rb_gc_mark_locations(VALUE*, VALUE*);
 void rb_mark_tbl(struct st_table*);