diff --git a/ChangeLog b/ChangeLog
index 3bbef3d696..67e03f9a60 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sat Mar  5 22:54:36 2011  CHIKANAGA Tomoyuki  <nagachika00@gmail.com>
+
+	* include/ruby/intern.h: fix a typo of prototype declaration.
+	  rb_mutex_try_lock -> rb_mutex_trylock [ruby-dev:43213]
+
 Sat Mar  5 19:44:03 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
 
 	* test/ruby/test_io.rb (TestIO#test_fcntl_lock): small clean up.
diff --git a/include/ruby/intern.h b/include/ruby/intern.h
index 7321a022a9..472166d995 100644
--- a/include/ruby/intern.h
+++ b/include/ruby/intern.h
@@ -802,7 +802,7 @@ VALUE rb_thread_io_blocking_region(rb_blocking_function_t *func, void *data1, in
 #define RUBY_UBF_PROCESS ((rb_unblock_function_t *)-1)
 VALUE rb_mutex_new(void);
 VALUE rb_mutex_locked_p(VALUE mutex);
-VALUE rb_mutex_try_lock(VALUE mutex);
+VALUE rb_mutex_trylock(VALUE mutex);
 VALUE rb_mutex_lock(VALUE mutex);
 VALUE rb_mutex_unlock(VALUE mutex);
 VALUE rb_mutex_sleep(VALUE self, VALUE timeout);