diff --git a/include/wx/os2/toolbar.h b/include/wx/os2/toolbar.h
index 608d65311a..edb8e0e785 100644
--- a/include/wx/os2/toolbar.h
+++ b/include/wx/os2/toolbar.h
@@ -13,6 +13,7 @@
 #define _WX_TOOLBAR_H_
 
 #if wxUSE_TOOLBAR
+#include "wx/timer.h"
 #include "wx/tbarbase.h"
 
 #define ID_TOOLTIMER                100