diff --git a/src/plugins/qmlprojectmanager/fileformat/qmlprojectitem.h b/src/plugins/qmlprojectmanager/fileformat/qmlprojectitem.h
index c91c36d4a3e..f3efc8010d5 100644
--- a/src/plugins/qmlprojectmanager/fileformat/qmlprojectitem.h
+++ b/src/plugins/qmlprojectmanager/fileformat/qmlprojectitem.h
@@ -32,6 +32,7 @@
 #define QMLPROJECTITEM_H
 
 #include <QObject>
+#include <QSet>
 #include <QStringList>
 #include <qdeclarative.h>