diff --git a/README.md b/README.md
index 26ae5cc..1943b10 100644
--- a/README.md
+++ b/README.md
@@ -100,8 +100,8 @@ See the PDF manual at <https://lukateras.github.io/nanoid.h/man.pdf>.
 $ nanoidgen [length]
 ```
 
-Generates a Nano ID of the default length, or the specified length within 1 and
-`GETENTROPY_MAX` (256), and prints it to the standard output.
+Generates a Nano ID of the default length (21), or the specified length within
+1 and `GETENTROPY_MAX` (256), and prints it to the standard output.
 
 [`getentropy(3)`]: https://pubs.opengroup.org/onlinepubs/9799919799/functions/getentropy.html
 [`nanoid(3)`]: https://lukateras.github.io/nanoid.h/man/nanoid.3.html
diff --git a/nanoidgen.1 b/nanoidgen.1
index 5435ccf..388285a 100644
--- a/nanoidgen.1
+++ b/nanoidgen.1
@@ -8,7 +8,7 @@
 .Op length
 .Sh DESCRIPTION
 .Nm
-generates a Nano ID of the default length, or the specified length within 1 and
+generates a Nano ID of the default length (21), or the specified length within 1 and
 .Dv GETENTROPY_MAX
 (256), and prints it to the standard output.
 .Sh EXIT STATUS