Installing Fedora 20 on my Mac Mini old version fails with the error "sda may not have enough space for grub2 to embed core img"

Hello to everyone. I'm trying to install Fedora 20 on my Mac Mini old version. I have got the 32 bit version because the 64 bit doesn't boot.... I have already installed refind...This is the disk partition table :

76.31 GB ATA Hitachi     sda

EFI                                 sda1     efi

Macintosh_HD                sda2     hfs+

available space = 39.91

When I do "make the partition automatically" and I get this error :

sda may not have enough space for grub2 to embed core img using the ext4 filesystem on the partition...

Do you have any idea about how to fix this error ? Thanks.