diff --git a/ChangeLog b/ChangeLog
index 4fb59025e2..c497a5aecf 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Wed Feb 20 14:28:00 2013  Zachary Scott  <zachary@zacharyscott.net>
+
+	* thread.c: Document ThreadGroup::Default
+
 Wed Feb 20 14:23:00 2013  Zachary Scott  <zachary@zacharyscott.net>
 
 	* thread.c: Grammar for #backtrace_locations and ::handle_interrupt
diff --git a/thread.c b/thread.c
index 66203bc449..d74356b879 100644
--- a/thread.c
+++ b/thread.c
@@ -3853,6 +3853,12 @@ static const rb_data_type_t thgroup_data_type = {
  *  were created.
  */
 
+/*
+ * Document-const: Default
+ *
+ *  The default ThreadGroup created when Ruby starts; all Threads belong to it
+ *  by default.
+ */
 static VALUE
 thgroup_s_alloc(VALUE klass)
 {