diff --git a/lib/config/configwriter.hpp b/lib/config/configwriter.hpp
index e27af011c..5eea742f6 100644
--- a/lib/config/configwriter.hpp
+++ b/lib/config/configwriter.hpp
@@ -25,6 +25,7 @@
 #include "base/array.hpp"
 #include "base/dictionary.hpp"
 #include <fstream>
+#include <set>
 
 namespace icinga
 {