diff --git a/secure/lib/libcipher/cipher.3 b/secure/lib/libcipher/cipher.3
index d361dd3a92f..a8dfab33f3b 100644
--- a/secure/lib/libcipher/cipher.3
+++ b/secure/lib/libcipher/cipher.3
@@ -43,8 +43,9 @@
 .Sh LIBRARY
 .Lb libcipher
 .Sh SYNOPSIS
+.Fd #include <unistd.h>
 .Ft int
-.Fn setkey "char *key"
+.Fn setkey "const char *key"
 .Ft int
 .Fn encrypt "char *block" "int flag"
 .Ft int