diff --git a/ChangeLog b/ChangeLog
index 448ad2321a..da81dc4606 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Sep 22 13:00:04 2016  Kazuhiro NISHIYAMA  <zn@mbf.nifty.com>
+
+	* gc.c (gc_start_internal): [DOC] methods without arguments
+	  like r56194. [Bug #12777]
+
 Wed Sep 21 17:43:53 2016  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* process.c (InitVM_process): Support CLOCK_MONOTONIC_RAW_APPROX,
diff --git a/gc.c b/gc.c
index 2eb049184c..770564126b 100644
--- a/gc.c
+++ b/gc.c
@@ -6574,7 +6574,8 @@ Init_stack(volatile VALUE *addr)
 /*
  *  call-seq:
  *     GC.start                     -> nil
- *     GC.garbage_collect           -> nil
+ *     ObjectSpace.garbage_collect  -> nil
+ *     include GC; garbage_collect  -> nil
  *     GC.start(full_mark: true, immediate_sweep: true)           -> nil
  *     ObjectSpace.garbage_collect(full_mark: true, immediate_sweep: true) -> nil
  *     include GC; garbage_collect(full_mark: true, immediate_sweep: true) -> nil