I have a CDT with field 1 as text data type and field 2 as integer data type

I am trying to import data from excel to database by using import excel to database smart service.

Excel file have same columns as field 1 and field 2. But If I am trying to use excel having field 2 value as null smart service is giving me error as :

incorrect integer value : for column "field2" at row 1

can someone please help ?