diff --git a/src/slic3r/GUI/DragDropPanel.hpp b/src/slic3r/GUI/DragDropPanel.hpp
index 7a10f4084..d98816483 100644
--- a/src/slic3r/GUI/DragDropPanel.hpp
+++ b/src/slic3r/GUI/DragDropPanel.hpp
@@ -6,6 +6,7 @@
 
 #include <wx/simplebook.h>
 #include <wx/dialog.h>
+#include <wx/sizer.h>
 #include <wx/timer.h>
 #include <vector>