monthStart lesser than dimension date in set analysis

[Morgoz]

Hello,

I want to show a count of number of errors detected before the start date of the current month in dimension.

This test works fine:

Count({<ERROR_DETECTION_DATE_QVD = {"$(='<='&'2021-05-01')"}>}ID_DQ_FACTS_QVD)

But this other code is not taking into account the condition of the monthStart, and it is returning all errors, not only the ones before monthStart:

Count({<ERROR_DETECTION_DATE_QVD = {"$(='<='&monthStart(EXEC_DATE_SQL_QVD))"}>}ID_DQ_FACTS_QVD)

EXEC_DATE_SQL_QVD is the current dimension date.

What am I doing wrong?

Thank you.