Include structure doesn't work. "Component called MANDT already exists. already exists" error

Hello,

I'm trying to append name1, werks from t001w and ktext, werks from t499s to object_tab but I get the error mentioned in the title. Any way I can avoid that? This is the relevant code:

Data: BEGIN OF object_tab OCCURS 0.

   INCLUDE STRUCTURE: t001w, t499s.

data END OF object_tab.

Thanks

Jim