integer overflow in reloption.h

When I compile postgresql now I get following message:

"../../../src/include/access/reloptions.h", line 45: warning: integer
overflow detected: op "<<"

The problem is on the following lines

typedef enum relopt_kind
{
...
RELOPT_KIND_MAX = (1 << 31)
}

enum is int datatype and 1 << 31 == -2147483648. It is reason why
compiler (sun studio) complains.

Is possible to change it to 1 << 30 to stop compiler generates noise?

Thanks Zdenek