diff --git a/ChangeLog b/ChangeLog
index bce6be9067..a066151215 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2017-06-12  Joseph Myers  <joseph@codesourcery.com>
+
+	[BZ #21550]
+	* signal/signal.h (sigwait): Only declare if [__USE_POSIX199506].
+
 2017-06-12  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* sysdeps/x86_64/multiarch/Makefile (sysdep_routines): Add
diff --git a/signal/signal.h b/signal/signal.h
index a43f8887e3..5ff94e0d25 100644
--- a/signal/signal.h
+++ b/signal/signal.h
@@ -240,12 +240,14 @@ extern int sigaction (int __sig, const struct sigaction *__restrict __act,
 extern int sigpending (sigset_t *__set) __THROW __nonnull ((1));
 
 
+# ifdef __USE_POSIX199506
 /* Select any of pending signals from SET or wait for any to arrive.
 
    This function is a cancellation point and therefore not marked with
    __THROW.  */
 extern int sigwait (const sigset_t *__restrict __set, int *__restrict __sig)
      __nonnull ((1, 2));
+# endif /* Use POSIX 1995.  */
 
 # ifdef __USE_POSIX199309
 /* Select any of pending signals from SET and place information in INFO.