Connecting with sftp using a proxy server

I am trying to connect to an external server using a proxy with the below command: sftp -v -o "ProxyCommand /usr/bin/nc -X connect -x proxyserver.com:8080 %h %p" user@server.com This isn't working. I get the below output: debug1: Reading configuration data /etc/ssh/ssh_config debug1: Applying options for * debug1: Executing proxy command: exec /usr/bin/nc -X connect -x proxyserver.com:8080 user@server.com debug1: permanently_drop_suid: 456876 bash: No such file or directory I think the command is formed correctly, it appears to be failing at the 'permanently_drop_suid' step. Does anybody have any idea what could be going wrong here? I can connect using WinSCP so the connection details are correct. Any assistance is greatly appreciated!