toggle button picture disappears when button is disabled

hi everyone

I'm writing an applciation in wich I use a toggle button. On the button is a picture:
me.ToggleButton.picture = new bitmap(application.startuppath & "\afbeeldingen\min.png"

Now the button has to be set disabled on startup. So i write the following code:
me.Togglebutton.enabled=false

It works, but the picture on my button becomes a gray rectangle??? (so I don't see my picture anymore when disabled)

Anyone any ideas

thx in advance