Bug - Bind variables not recognised in model clause - Toad 12.10.0.30

It appears there is a bug in the model clause where bind variables are not picked up for value entry at execution time. See the following simple example - if run in Toad, the window pops up to accept the bind variable value input, however the bind variable isn't listed.

Select *
  From dual
 Model 
   Dimension by (dummy d)
   Measures ('A' v)
   Rules (
     v['X'] = :val
   );