diff --git a/WINGs/usleep.c b/WINGs/usleep.c
index fcdf3277..99d07912 100644
--- a/WINGs/usleep.c
+++ b/WINGs/usleep.c
@@ -2,6 +2,7 @@
 #include <errno.h>
 #include <time.h>
 
+#include "WUtil.h"
 #include "wconfig.h"
 
 void wusleep(unsigned int usec)