diff --git a/include/common/ist.h b/include/common/ist.h
index 7c60c68..cfab1e3 100644
--- a/include/common/ist.h
+++ b/include/common/ist.h
@@ -30,6 +30,7 @@
 
 #include <ctype.h>
 #include <string.h>
+#include <unistd.h>
 
 #include <common/config.h>