diff --git a/src/core/core.h b/src/core/core.h
index ec7b381e..62346c64 100644
--- a/src/core/core.h
+++ b/src/core/core.h
@@ -24,6 +24,8 @@
 #include "corestructs.h"
 #include "toxid.h"
 
+#include <functional>
+
 #include <tox/tox.h>
 
 #include <QMutex>