diff --git a/include/confirm.h b/include/confirm.h
index 7f33d4f127..8ff4c830f0 100644
--- a/include/confirm.h
+++ b/include/confirm.h
@@ -33,6 +33,7 @@
 
 #include <wx/richmsgdlg.h>
 #include <vector>
+#include <functional>
 
 class wxCheckBox;
 class wxStaticBitmap;