diff --git a/lib/methods/utilityfuncs.cpp b/lib/methods/utilityfuncs.cpp
index 290ab1576..4a5ae82e5 100644
--- a/lib/methods/utilityfuncs.cpp
+++ b/lib/methods/utilityfuncs.cpp
@@ -25,6 +25,7 @@
 #include "base/dictionary.h"
 #include <boost/regex.hpp>
 #include <algorithm>
+#include <set>
 
 using namespace icinga;