diff --git a/chrony.texi b/chrony.texi
index a284741..b33f971 100644
--- a/chrony.texi
+++ b/chrony.texi
@@ -1458,6 +1458,8 @@ An example of the commandkey command is
 commandkey 20
 @end example
 
+By default, the key number is 0.
+
 In the key file (see the keyfile command) there should be a line of
 the form