Error when using the hashcat utility .pcap to .hccapx file

Hi, I'm using the hashcat utilty: https://hashcat.net/cap2hccapx/ I'm capturing packets using the latest version of Wireshark and I'm saving the packets in the Wireshark/tcpdump format. I get this error when I use the utility: 

in/7995_1521602201.cap: Unsupported linktype detected

I found a similar thread to my post, but the answer did not mean anything to me.

Thanks,