diff --git a/lib/libc/stdlib/getopt.3 b/lib/libc/stdlib/getopt.3
index 76ed7d5d2436..9ffe5674627d 100644
--- a/lib/libc/stdlib/getopt.3
+++ b/lib/libc/stdlib/getopt.3
@@ -74,7 +74,7 @@ word, or
 .Dv NULL
 if there were no more characters in the current word.
 This is a
-.Nx
+.It Tn GNU
 extension.
 For example, an option string
 .Li \&"x"