diff --git a/headers/os/interface/OutlineListView.h b/headers/os/interface/OutlineListView.h
index e553bd345e..87b2be2d2c 100644
--- a/headers/os/interface/OutlineListView.h
+++ b/headers/os/interface/OutlineListView.h
@@ -8,8 +8,12 @@
 
 #include <ListView.h>
 
-class BListItem;
 
+class BList;
+class BListItem;
+class BMessage;
+class BPoint;
+class BRect;
 
 class BOutlineListView : public BListView {
 public: