[Exim] quote_mysql & underscores

Hi!

I was wondering if its normal behavour that quote_mysql places a backslash
infront of an underline?

(simplified)

query = "select username from aliases where alias =
'${quote_mysql:$local_part}'"

so when $loca_part is example_user@??? exim extracts that line to

select username from aliases where alias = 'example\_user'

The query fails on that ofcourse because the alias is 'example_user' and not
'example\_user'.

Is this normal?

EG