diff --git a/gtk2_ardour/canvas-waveview.c b/gtk2_ardour/canvas-waveview.c
index 193b3cd68a..db95732b16 100644
--- a/gtk2_ardour/canvas-waveview.c
+++ b/gtk2_ardour/canvas-waveview.c
@@ -24,6 +24,7 @@
 #include <cairo.h>
 #include <string.h>
 #include <limits.h>
+#include <unistd.h>
 
 #include "ardour/dB.h"