diff --git a/Documentation/sched-design-CFS.txt b/Documentation/sched-design-CFS.txt
index 16feebb7bdc077f334964443235996a187a4cf90..84901e7c05084e1f767d024b7f06cde1f19d6854 100644
--- a/Documentation/sched-design-CFS.txt
+++ b/Documentation/sched-design-CFS.txt
@@ -83,7 +83,7 @@ Some implementation details:
    CFS uses nanosecond granularity accounting and does not rely on any
    jiffies or other HZ detail. Thus the CFS scheduler has no notion of
    'timeslices' and has no heuristics whatsoever. There is only one
-   central tunable:
+   central tunable (you have to switch on CONFIG_SCHED_DEBUG):
 
          /proc/sys/kernel/sched_granularity_ns