diff --git a/Documentation/trace/histogram.rst b/Documentation/trace/histogram.rst
index c1b685a38f6b..87bd772836c0 100644
--- a/Documentation/trace/histogram.rst
+++ b/Documentation/trace/histogram.rst
@@ -39,7 +39,7 @@ Documentation written by Tom Zanussi
   will use the event's kernel stacktrace as the key.  The keywords
   'keys' or 'key' can be used to specify keys, and the keywords
   'values', 'vals', or 'val' can be used to specify values.  Compound
-  keys consisting of up to two fields can be specified by the 'keys'
+  keys consisting of up to three fields can be specified by the 'keys'
   keyword.  Hashing a compound key produces a unique entry in the
   table for each unique combination of component keys, and can be
   useful for providing more fine-grained summaries of event data.