I have problem with tBitmaps

why work
     bt:=tSpeedButton.create(app);
     bt.Glyph:=TBitmap.Create;
     bt.glyph.LoadFromLAZARUSResource('spin');
and don work (dont paint bitmap - only draw 1 pixel)
     bt:=tSpeedButton.create(app);
     bbt:=TBitmap.Create;
     bbt.LoadFromLAZARUSResource('spin');
    bt.glyph:=bbt

when I define BITMAPSHARINGWORKS

when definitions is OFF all is OK

some thing is with function ASSIGN but I can't find what.

Darek