diff --git a/include/AvatarProvider.h b/include/AvatarProvider.h
index 44bf1ad2..77f9ebb4 100644
--- a/include/AvatarProvider.h
+++ b/include/AvatarProvider.h
@@ -20,6 +20,7 @@
 #include <QImage>
 #include <QSharedPointer>
 #include <QUrl>
+#include <functional>
 
 class MatrixClient;
 class TimelineItem;