Validate elements for Int32 and blanks

Hello!
I am im****ting a flat file where some elements are Int32 values. These 
elements have values most of the time, but sometimes there are just
blanks. 
Now the message is suspended because the string '' is not an Int32
datatype. 
But I want to allow this :-) I want the schema to validate for and allow 
Int32 or blanks.

I have set nillable=true and MinOccurs=0 on the element. On the schema 
definition I have set Early Terminate Optional fields=true, Parser 
Optimization = Complexity and lookahead depth=0. Now I don't know what
more 
to try in order to get this working.

This will work if I change the datatype to string, but I don't want to
allow 
text in the element.

Many thanks in advance!
Best regards,
Vemund