diff --git a/tools/perf/Documentation/perf-lock.txt b/tools/perf/Documentation/perf-lock.txt
index 921de25..4a26a2f 100644
--- a/tools/perf/Documentation/perf-lock.txt
+++ b/tools/perf/Documentation/perf-lock.txt
@@ -24,8 +24,8 @@
 
   'perf lock report' reports statistical data.
 
-OPTIONS
--------
+COMMON OPTIONS
+--------------
 
 -i::
 --input=<file>::
@@ -39,6 +39,14 @@
 --dump-raw-trace::
         Dump raw trace in ASCII.
 
+REPORT OPTIONS
+--------------
+
+-k::
+--key=<value>::
+        Sorting key. Possible values: acquired (default), contended,
+        wait_total, wait_max, wait_min.
+
 SEE ALSO
 --------
 linkperf:perf[1]
diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
index e00d938..2e93f99 100644
--- a/tools/perf/builtin-lock.c
+++ b/tools/perf/builtin-lock.c
@@ -893,7 +893,7 @@
 
 static const struct option report_options[] = {
 	OPT_STRING('k', "key", &sort_key, "acquired",
-		    "key for sorting"),
+		    "key for sorting (acquired / contended / wait_total / wait_max / wait_min)"),
 	/* TODO: type */
 	OPT_END()
 };