- dcp.write_xml (_film->interop () ? dcp::INTEROP : dcp::SMPTE, meta, _film->is_signed() ? make_signer () : shared_ptr<const dcp::Signer> ());
+ shared_ptr<const dcp::Signer> signer;
+ if (_film->is_signed ()) {
+ signer = Config::instance()->signer ();
+ /* We did check earlier, but check again here to be on the safe side */
+ if (!signer->valid ()) {
+ throw InvalidSignerError ();
+ }
+ }
+
+ dcp.write_xml (_film->interop () ? dcp::INTEROP : dcp::SMPTE, meta, signer);