diff --git a/libao/libao.rkt b/libao/libao.rkt
index 2339f1a..ad7eba6 100644
--- a/libao/libao.rkt
+++ b/libao/libao.rkt
@@ -176,7 +176,7 @@
           (reverse bytes)
           bytes))))
 
-(define (ao-play handle at-time-in-s buffer)
+(define (ao-play handle at-time-in-s music-duration-s buffer)
   (let* ((bytes-per-sample (ao-handle-bytes-per-sample handle))
          (bits (ao-handle-bits handle))
          (channels (ao-handle-channels handle))
@@ -212,10 +212,12 @@
       (if (eq? libao-async-mode 'ffi)
           (ffi:ao_play_async (ao-handle-async-player handle)
                              (exact->inexact at-time-in-s)
+                             (exact->inexact music-duration-s)
                              audio-buf-len
                              audio)
           (scm:ao_play_async (ao-handle-async-player handle)
                              (exact->inexact at-time-in-s)
+                             (exact->inexact music-duration-s)
                              audio-buf-len
                              audio)
           )