diff --git a/ChangeLog b/ChangeLog
index 5f797204b0..56af5bf414 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Mon Jan  4 15:44:37 2016  Sho Hashimoto  <sho-h@ruby-lang.org>
+
+	* variable.c (rb_mod_deprecate_constant): [DOC] added
+	  documentation for Module#deprecate_constant. [ci skip]
+
 Mon Jan  4 15:36:38 2016  Sho Hashimoto  <sho-h@ruby-lang.org>
 
 	* thread_sync.c: [DOC] remove SizedQueue#close argument.
diff --git a/variable.c b/variable.c
index b0334618bf..047dbc7e67 100644
--- a/variable.c
+++ b/variable.c
@@ -2719,6 +2719,13 @@ rb_mod_public_constant(int argc, const VALUE *argv, VALUE obj)
     return obj;
 }
 
+/*
+ *  call-seq:
+ *     mod.deprecate_constant(symbol, ...)    => mod
+ *
+ *  Makes a list of existing constants deprecated.
+ */
+
 VALUE
 rb_mod_deprecate_constant(int argc, const VALUE *argv, VALUE obj)
 {