diff --git a/ChangeLog b/ChangeLog
index 3ea69106cc..f2fe71b045 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sat Aug 14 21:04:28 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* thread.c (rb_gc_mark_threads): deprecated.
+
 Sat Aug 14 19:12:10 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* ext/{coverage,objspace}/extconf.rb ($INCFLAGS): explicitly add
diff --git a/gc.c b/gc.c
index 1eaa3d066b..47eb3a668e 100644
--- a/gc.c
+++ b/gc.c
@@ -2347,7 +2347,6 @@ gc_marks(rb_objspace_t *objspace)
 
     mark_current_machine_context(objspace, th);
 
-    rb_gc_mark_threads();
     rb_gc_mark_symbols();
     rb_gc_mark_encodings();
 
diff --git a/include/ruby/intern.h b/include/ruby/intern.h
index 0f9b8cb0a4..0ae4d47157 100644
--- a/include/ruby/intern.h
+++ b/include/ruby/intern.h
@@ -333,7 +333,7 @@ void rb_exec_end_proc(void);
 void ruby_finalize(void);
 NORETURN(void ruby_stop(int));
 int ruby_cleanup(volatile int);
-void rb_gc_mark_threads(void);
+DEPRECATED(void rb_gc_mark_threads(void));
 void rb_thread_schedule(void);
 void rb_thread_wait_fd(int);
 int rb_thread_fd_writable(int);
diff --git a/thread.c b/thread.c
index 49d4d28df0..6c783c9dc9 100644
--- a/thread.c
+++ b/thread.c
@@ -1326,7 +1326,7 @@ rb_threadptr_execute_interrupts(rb_thread_t *th)
 void
 rb_gc_mark_threads(void)
 {
-    /* TODO: remove */
+    rb_bug("deprecated function rb_gc_mark_threads is called");
 }
 
 /*****************************************************/