diff --git a/Extras/glui/GL/glui.h b/Extras/glui/GL/glui.h
index 4b268066e..a073ab2c2 100644
--- a/Extras/glui/GL/glui.h
+++ b/Extras/glui/GL/glui.h
@@ -321,6 +321,8 @@ class GLUI_FileBrowser;
 class GLUI_Scrollbar;
 class GLUI_Listbox;
 class GLUI_List;
+class GLUI_Rollout;
+class GLUI_Tree;
 
 
 /**