photo grayscale

I'm using 8.5.2 and can't seem to get photo's grayscale command
to return anything but all black. Is this a bug or am I doing
something
wrong?

Here's a code snippet showing the problem:

package require Tk
image create photo ::img::org -width 120 -height 120
label .org -image ::img::org -relief ridge -text Original -compound
top
image create photo ::img::clone -width 120 -height 120
label .clone -image ::img::clone -relief ridge -text Clone -compound
top
image create photo ::img::gray -width 120 -height 120
label .gray -image ::img::gray -relief ridge -text Grayscale -compound
top
eval pack [winfo child .] -side top

::img::org put red -to 0 0 40 120 ;# Create a simple gif with
3 colors
::img::org put green -to 40 0 80 120
::img::org put blue -to 80 0 120 120
::img::clone put [::img::org data]
::img::gray put [::img::org data -grayscale]


Thanks,
Keith
.