diff --git a/dios/include/unistd.h b/dios/include/unistd.h
index 8cdcace7ac29e8ad1bc776b3e7dc0ceb681c36f4..c453f656c5bd5a2e5dfe20971a9f811631717852 100644
--- a/dios/include/unistd.h
+++ b/dios/include/unistd.h
@@ -1,5 +1,6 @@
 // -*- C++ -*- (c) 2015 Jiří Weiser
 
+#include <bits/confname.h>
 #include <sys/types.h>
 #include <sys/cdefs.h>
 #include <sys/hostabi.h>