Failed Import of Multi-select custom field ending on a comma (the separator)

Multi Select Custom field has been defined with following values

CustomFIeld:
valueX labelX
valueY labelY
valueZ labelZ

The imported data contains a column which is mapped onto this CustomField.
This column contains values like

valueX,
valueY,valueZ,
valueX,valueZ,

i.o.w : the fields to import have an ending ',' which is apparantly blocking the import.