QFile::map call fails when size is greater than 524288 (512KB)

map call fails when size is greater than 524288 (512KB).
We have applications that need to map files of size close to 1MB or greater so this needs to work for larger size than 512KB

// QFile* file = ...;

PVOID pv = NULL;
qint64 offset = 0;
qint64 size;

// Success case, pv returned below is non-NULL

size = 500000;
pv = file->map(offset, size);

// Failure case, pv returned below is NULL

size = 600000;
pv = file->map(offset, size);

Do let me know if you need more information.