Q: Windows 8.1 install on iMac with fusion drive, GPT partition error

Hello,

I have been trying to install windows via bootcamp on my iMac and cannot seem to fix the 'Windows cannot be installed to this disc. The selected disc is of the GPT partition style' error.I have a late 2013 model iMac with a 1TB fusion drive. I am currently running OSX Mavericks and I am trying to instal Windows 8.1 using a USB connected superdrive. I am using bootcamp assistant to download the windows drivers and partition the drive. The target size of the Windows partition is about 40GB.

I am successfully completing all steps until I am in the Windows install and select the partition on which Windows should be installed. I get the error 'Windows cannot be installed to this disc. The selected disc is of the GPT partition style.' I have formatted the partition, but I still get the same error. The bootcamp partition is disk1s4.

Can anyone recommend what I can do to overcome this issue? I've been searching for an answer and have tried reformatting within disk utility and cannot get past this step. Thank you in advance!