String does not evolve into BigDecimal

Numeric strings should evolve into BigDecimal.
 
The following does not work:
 
 

class Band

  field :sales, type: BigDecmial

end

Band.create!(sales: BigDecimal(100))

Band.where(sales: '100').count #=> 0  incorrect!

 
 
Note that this works correctly for Integer, Float, etc. so it's clearly a bug.