diff --git a/include/boost/config/posix_features.hpp b/include/boost/config/posix_features.hpp
index b0580f22..be1e0216 100644
--- a/include/boost/config/posix_features.hpp
+++ b/include/boost/config/posix_features.hpp
@@ -32,11 +32,16 @@
 
       // BOOST_HAS_NANOSLEEP:
       // This is predicated on _POSIX_TIMERS or _XOPEN_REALTIME:
-      // BOOST_HAS_CLOCK_GETTIME:
-      // This is predicated on _POSIX_TIMERS or _XOPEN_REALTIME:
 #     if (defined(_POSIX_TIMERS) && (_POSIX_TIMERS+0 >= 0)) \
              || (defined(_XOPEN_REALTIME) && (_XOPEN_REALTIME+0 >= 0))
 #        define BOOST_HAS_NANOSLEEP
+#     endif
+
+      // BOOST_HAS_CLOCK_GETTIME:
+      // This is predicated on _POSIX_TIMERS (also on _XOPEN_REALTIME
+      // but at least one platform - linux - defines that flag without
+      // defining clock_gettime):
+#     if (defined(_POSIX_TIMERS) && (_POSIX_TIMERS+0 >= 0))
 #        define BOOST_HAS_CLOCK_GETTIME
 #     endif