--- a/sandbox/linux/services/credentials.h
+++ b/sandbox/linux/services/credentials.h
@@ -13,6 +13,7 @@
 
 #include <string>
 #include <vector>
+#include <unistd.h>
 
 #include "sandbox/linux/system_headers/capability.h"
 #include "sandbox/sandbox_export.h"
