failed to compile a sieve script with optional include

Hi,

I am trying to compile the following sieve script:

require [ "variables", "include", "relational", "imapsieve" ];

global "importing";

include :personal :optional "pre-sent-checks";

if string :count "eq" "${importing}" "1" { keep; stop; }

But I have this error:

sent-checks: line 15: error: include: personal location for included script `pre-sent-checks' is unavailable (contact system administrator for more information). sent-checks: error: validation failed. sievec(root): Fatal: failed to compile sieve script 'sent- checks.sieve'

What should I do to compile a script with an optional user script, please ?

Thanks