ECPG: How to use #define and string host variable

I want to declare a character string's
length as a #define and below gives me:

ERROR: parse error, expecting `CVARIABLE' or `ICONST' or `']'' or `'('
' at or near "MAX"

#define MAX 10

EXEC SQL BEGIN DECLARE SECTION;
char t[MAX];
EXEC SQL END DECLARE SECTION;

How do I make the precompiler see the define?

Thanks.