length checking and encoding in postgresql 8.1.4

I got a field with a datatype of varchar(40) in one of my table

client_encoding = LATIN9

When I use COPY to transfer records to my table
I got an error message "Error: value too long for type character varying(40)"

When I check the offending record it seems that one of the character
in the field contains N (with a wave-like at top) . The actual length
of the string is 40 so it should be accepted considering the fact that
it is properly translated as that character mentioned earlier.

So far other Pgsql 8.1.3 accepts the record.