Point of the semicolon in this shellshock attack

I was reviewing a shellshock attack and didn't understand this piece of code: curl -v http://localhost/cgi-bin/shellshock.cgi -H "custom:() { ignored; }; echo Content-Type: text/html; echo ; /bin/cat /etc/passwd " The part that I don't understand is the function of the echo ; in the actually executed command on the remote machine between echoing the Content-Type and /bin/cat on /etc/passwd. What is the function of echo ; here? Thanks.