diff --git a/src/tiocgwinsz.scm b/src/tiocgwinsz.scm
index fb77d66..8d00ff8 100644
--- a/src/tiocgwinsz.scm
+++ b/src/tiocgwinsz.scm
@@ -25,8 +25,11 @@
 
 (declare (unit tiocgwinsz))
 
-(module
+(import duck)
+
+(module*
  tiocgwinsz
+ #:doc ("TTY terminal size support.")
  (
   tiocgwinsz
   )
@@ -50,7 +53,8 @@ if (ioctl(0, TIOCGWINSZ, &wss) == 0) {
 "
     ))
 
- (define (tiocgwinsz)
+ (define/doc (tiocgwinsz)
+   ("Returns the number of terminal rows and columns.")
    (let ((res (tiocgwinsz-ioctl)))
      (values (bitwise-and res #xffff)
 	     (arithmetic-shift res -16))))