ActiveRecord and BigDecimal problem with decimal point

We are using database with Czech Collation (Locales) and Czech language uses comma as decimal point. ActiveRecord (and BigDecimal) are not written for using comma. So, when another character than digit or point appears on input, input is stopped and previous parsed text is returned as number.
We have to compute with prices that are decimal. In database is stored something like 123,45 but after calling

> Amount.find(1).value

we received 123 instead of 123.45 (#<BigDecimal:4b5850c,'0.12345e3',8(12)>)
I traced ActiveRecord and found that method find (its internal implementation) uses method instantiate and it calls object.instance_variable_set("@attributes", record) and this method is just stub for C runtime libraries.
So I created solution - override method instance_variable_set in model class Amount like this:

def instance_variable_set symbol, obj
 super
 if symbol == "@attributes"
   input = obj["value"]
   unless input.nil? or input.index(",").nil?
     input[input.index(",")] = "."
     @value = BigDecimal.new(input)
   end
 end
end

Any better solution?