diff --git a/include/villas/config.hpp b/include/villas/config.hpp
index 5c6c538d2..3b8867ca8 100644
--- a/include/villas/config.hpp
+++ b/include/villas/config.hpp
@@ -24,6 +24,7 @@
 #pragma once
 
 #include <cstdio>
+#include <unistd.h>
 
 #include <functional>
 #include <regex>