I have been running Varnish on my production server successfully for several weeks now. Now I'm trying to configure Varnish to use a second backend for certain requests. My original working VCL (/etc/varnish/default.vcl) begins like this:

backend default {
  .host = "127.0.0.1";
  .port = "8080";
}

...rest of VCL...

And I'm changing it to:

backend default {
  .host = "127.0.0.1";
  .port = "8080";
}

backend backend2 {
  .host = "12.34.56.78";
  .port = "80";
}

...rest of VCL...

When I reload the VCL file, I get the following:

Command failed with error code 106
Failed to reload /etc/varnish/default.vcl.

Any idea what the error could be, or how I can get more information on the problem?