diff --git a/audio-placed-player.rkt b/audio-placed-player.rkt
index 8287a43..2e08e47 100644
--- a/audio-placed-player.rkt
+++ b/audio-placed-player.rkt
@@ -8,7 +8,9 @@
          early-return
          )
 
-(provide placed-player)
+(provide placed-player
+         audio-known-exts?
+         )
 
 (define get-current-seconds current-seconds)
 
diff --git a/audio-player.rkt b/audio-player.rkt
index ae98263..303a62d 100644
--- a/audio-player.rkt
+++ b/audio-player.rkt
@@ -29,6 +29,7 @@
          audio-file
          audio-play?
          audio-buf-seconds!
+         audio-known-exts?
          )
 
 (define-struct audio-play