diff --git a/resolver.c b/resolver.c
index 3d8935e..6980d93 100644
--- a/resolver.c
+++ b/resolver.c
@@ -13,6 +13,7 @@
 #include <netdb.h>
 #include <errno.h>
 #include <string.h>
+#include <unistd.h>
 
 #include "ns_hash.h"
 #include "iftop.h"