diff --git a/ChangeLog b/ChangeLog
index 5e6450905e..fae6ff31e4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2018-02-20  Rical Jasan  <ricaljasan@pacific.net>
+
+	* manual/creature.texi (_ISOC99_SOURCE): Update the dated
+	description.
+
 2018-02-20  Rical Jasan  <ricaljasan@pacific.net>
 
 	* manual/creature.texi (_POSIX_C_SOURCE): Document special values
diff --git a/manual/creature.texi b/manual/creature.texi
index 483bf85ad7..fe7a7790a2 100644
--- a/manual/creature.texi
+++ b/manual/creature.texi
@@ -167,10 +167,9 @@ This macro was introduced as part of the Large File Support extension
 
 @defvr Macro _ISOC99_SOURCE
 @standards{GNU, (none)}
-Until the revised @w{ISO C} standard is widely adopted the new features
-are not automatically enabled.  @Theglibc{} nevertheless has a complete
-implementation of the new standard and to enable the new features the
-macro @code{_ISOC99_SOURCE} should be defined.
+If this macro is defined, features from ISO C99 are included.  Since
+these features are included by default, this macro is mostly relevant
+when the compiler uses an earlier language version.
 @end defvr
 
 @defvr Macro _ISOC11_SOURCE