diff --git a/time.c b/time.c
index 19517a785d..846ff3db16 100644
--- a/time.c
+++ b/time.c
@@ -4612,10 +4612,7 @@ time_strftime(VALUE time, VALUE format)
     return str;
 }
 
-/*
- * undocumented
- */
-
+/* :nodoc: */
 static VALUE
 time_mdump(VALUE time)
 {
@@ -4713,13 +4710,7 @@ time_mdump(VALUE time)
     return str;
 }
 
-/*
- * call-seq:
- *   time._dump   -> string
- *
- * Dump _time_ for marshaling.
- */
-
+/* :nodoc: */
 static VALUE
 time_dump(int argc, VALUE *argv, VALUE time)
 {
@@ -4731,10 +4722,7 @@ time_dump(int argc, VALUE *argv, VALUE time)
     return str;
 }
 
-/*
- * undocumented
- */
-
+/* :nodoc: */
 static VALUE
 time_mload(VALUE time, VALUE str)
 {
@@ -4851,13 +4839,7 @@ end_submicro: ;
     return time;
 }
 
-/*
- * call-seq:
- *   Time._load(string)   -> time
- *
- * Unmarshal a dumped Time object.
- */
-
+/* :nodoc: */
 static VALUE
 time_load(VALUE klass, VALUE str)
 {
diff --git a/vm_method.c b/vm_method.c
index 9727a2ada8..4b4be139a7 100644
--- a/vm_method.c
+++ b/vm_method.c
@@ -1505,6 +1505,8 @@ obj_respond_to(int argc, VALUE *argv, VALUE obj)
  *  call-seq:
  *     obj.respond_to_missing?(symbol, include_all) -> true or false
  *
+ *  DO NOT USE THIS DIRECTLY.
+ *
  *  Hook method to return whether the _obj_ can respond to _id_ method
  *  or not.
  *