diff --git a/project/undo.h b/project/undo.h
index 7e395ff10..e6d301eda 100644
--- a/project/undo.h
+++ b/project/undo.h
@@ -2,8 +2,8 @@
 #define UNDO_H
 
 class QTreeWidgetItem;
-class Clip;
-class Sequence;
+struct Clip;
+struct Sequence;
 
 #include <QUndoStack>
 #include <QUndoCommand>