diff --git a/src/libs/timeline/timelinetheme.h b/src/libs/timeline/timelinetheme.h
index eb292ffc2f7..24412b757ac 100644
--- a/src/libs/timeline/timelinetheme.h
+++ b/src/libs/timeline/timelinetheme.h
@@ -27,7 +27,7 @@
 
 #include "timeline_global.h"
 
-class QQmlEngine;
+QT_FORWARD_DECLARE_CLASS(QQmlEngine)
 
 namespace Timeline {