diff --git a/libao2/pl_surround.c b/libao2/pl_surround.c
index e7cae5109d..387e524a3e 100644
--- a/libao2/pl_surround.c
+++ b/libao2/pl_surround.c
@@ -28,6 +28,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <unistd.h>
 
 #include "audio_out.h"
 #include "audio_plugin.h"